Positive Electrode Active Substance for All Solid-State Lithium Secondary Battery

ABSTRACT

A positive electrode active substance for an all solid-state lithium secondary battery having an operating potential of 4.5 V or more at a metal Li reference potential, wherein the surface of the present core particles composed of a spinel-type lithium manganese-containing composite oxide containing at least Li, Mn, O, and two or more elements other than these is coated with an amorphous compound containing Li, A, where A represents one element or a combination of two or more elements selected from the group consisting of Ti, Zr, Ta, Nb, Zn, W, and Al, and O. Primary particles of the present core particles are composed of a polycrystal. The D50 is 0.5-9 μm, the value of (|mode diameter−D50|/mode diameter)×100 is 0 to 25%, the value of (|mode diameter−D10|/mode diameter)×100 is 20-58%, and the value of the average primary particle diameter/D50 is 0.20-0.99.

TECHNICAL FIELD

The present invention relates to a positive electrode active substancethat can be suitably used for a lithium secondary battery using a solidelectrolyte (referred to as “all solid-state lithium secondarybattery”). Particularly, the present invention relates to a 5 V-classpositive electrode active substance having an operating potential of 4.5V or more at a metal Li reference potential.

BACKGROUND ART

Lithium secondary batteries have characteristics of high energy density,long life, and the like. Therefore, the lithium secondary batteries arewidely used as power supplies for electric appliances such as videocameras, portable electronic devices such as laptop computers and mobiletelephones, and electric tools such as power tools. Recently, thelithium secondary batteries are also applied to large-sized batteriesthat are mounted in electric vehicles (EVs), hybrid electric vehicles(HEVs), and the like.

The lithium secondary batteries are secondary batteries having astructure in which, at the time of charging, lithium begins to dissolveas ions from the positive electrode and moves to the negative electrodeto be stored therein, and at the time of discharging, the lithium ionsreturn from the negative electrode to the positive electrode; and it isknown that the higher energy density is attributable to the electricpotential of the positive electrode material.

The lithium secondary battery of this kind is generally constituted of apositive electrode, a negative electrode, and an ion conducting layerinserted between both of the electrodes. As the ion conducting layer, aseparator constituted of a porous film such as polyethylene orpolypropylene, which is filled with a non-aqueous electrolytic solution,is generally used.

However, since such a flammable organic electrolytic solution is used,it is required to improve the structure and material for preventingvolatilization and leakage, and also, it is required to install a safetydevice for suppressing an increase in temperature at the time of a shortcircuit and to improve the structure and material for preventing a shortcircuit.

In contrast, an all solid-state lithium secondary battery does notrequire a flammable organic electrolyte solution. Therefore,simplification of safety devices can be attempted, and the battery canbe excellent in terms of production cost and productivity. Also, thebattery has a feature that the solid electrolyte can be laminated inseries in a cell, to achieve a high voltage battery.

Furthermore, in the solid electrolyte of this kind, since nothing but anion moves, side reactions caused by movement of anions do not occur, andit is expected that this leads to improvement of safety and durability.

The solid electrolyte to be used in the all solid-state lithiumsecondary battery is required to have high ionic conductivity as far aspossible and to be stable chemically and electrochemically. For example,lithium halide, lithium nitride, lithium acid salt, derivatives of thesecompounds, and the like are known as candidate materials for the solidelectrolyte.

On the other hand, the solid electrolyte and the positive electrodeactive substance to be used in the all solid-state lithium secondarybattery have a problem in that a high resistant layer is formed byreacting each other, and thus the interfacial resistance becomes large.Therefore, proposals for improving the interface have been disclosed.

For example, in regard to a positive electrode active substance that canbe used for an all solid-state lithium secondary battery, PatentDocument 1 discloses that a LiNbO₃ coating layer is formed on thesurface of the positive electrode active substance, and, by using such apositive electrode active substance, the output characteristics of theall solid-battery can be improved by interposing a lithiumion-conducting oxide layer between the interfaces of the positiveelectrode active substance and a solid electrolyte.

Further, Patent Document 2 discloses an active substance powder that hasa coating layer containing LiNbO₃ on the surface of the active substanceparticles capable of absorbing and desorbing lithium ions at a potentialof 4.5 or more based on Li.

CITATION LIST Patent Document

Patent Document 1: International Publication No. WO 2007/4590

Patent Document 2: Japanese Patent Laid-Open No. 2015-179616

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

As disclosed in Patent Document 2, it is confirmed that when a lithiumion-conducting oxide layer such as LiNbO₃ is formed on the surface of apositive electrode active substance capable of absorbing and desorbinglithium ions at a potential of 4.5 V or more based on Li (referred to as“5 V-class positive electrode active substance”), and interposed betweenthe interfaces of the 5 V-class positive electrode active substance anda solid electrolyte, the battery capacity can be further increased.

However, when investigating a spinel-type composite oxide containing Li,Mn, O, and two or more elements other than these, it is found, in the 5V-class positive electrode active substance, that the resistance cannotbe suppressed while enhancing the ionic conductivity only by forming alithium ion-conducting oxide layer such as LiNbO₃, and thus the ratecharacteristics and cycle characteristics cannot be improved. It isassumed that this is because the interfacial resistance between theactive substance and the solid electrolyte is remarkably increased whenusing the 5 V-class positive electrode active substance.

Thus, the present invention is to provide a novel positive electrodeactive substance capable of suppressing the resistance and improving therate characteristics and cycle characteristics while enhancing the ionicconductivity, in which the surface of particles composed of aspinel-type composite oxide containing Li, Mn, O, and two or moreelements other than these is coated with a lithium ion-conducting oxide.Particularly, the present invention focuses on reducing the contactresistance between the positive electrode active substance and the solidelectrolyte, and is to provide a positive electrode active substancecapable of maintaining a high operating voltage during discharge.

Means for Solving Problem

The present invention proposes a positive electrode active substance foran all solid-state lithium secondary battery having an operatingpotential of 4.5 V or more at a metal Li reference potential, whereinthe surface of particles (also referred to as “present core particles”)composed of a spinel-type lithium manganese-containing composite oxidecontaining at least Li, Mn, O, and two or more elements other than theseis coated with an amorphous compound containing Li, A (A represents oneelement or a combination of two or more elements selected from the groupconsisting of Ti, Zr, Ta, Nb, Zn, W, and Al), and O; and primaryparticles of the present core particles are composed of a polycrystal;

wherein, with regard to a D50, a mode diameter, and a D10 of thepositive electrode active substance according to a measurement of avolume-based particle size distribution obtained via measurements by alaser diffraction scattering-type particle size distribution measurementmethod (referred to as “D50”, “mode diameter”, and “D10”, respectively),the D50 is 0.5 to 9 μm, a percentage of a ratio of the absolute value ofthe difference between the mode diameter and the D50 relative to themode diameter ((|mode diameter−D50|/mode diameter)×100) is 0 to 25%, apercentage of a ratio of the absolute value of the difference betweenthe mode diameter and the D10 relative to the mode diameter ((|modediameter−D10|/mode diameter)×100) is 20 to 58%; and wherein a ratio(average primary particle diameter/D50) of an average primary particlediameter of the positive electrode active substance, which is calculatedfrom a scanning-type electron microscope (SEM) image obtained by a SEM,relative to the D50 is 0.20 to 0.99.

Here, the term |mode diameter−D50| means an absolute value of (modediameter−D50), and the term |mode diameter−D10| means an absolute valueof (mode diameter−D10) (the same applies to the case that will bedescribed below).

Also, the present invention proposes a positive electrode activesubstance for an all solid-state lithium secondary battery having anoperating potential of 4.5 V or more at a metal Li reference potential,wherein the surface of the present core particles is coated with anamorphous compound containing Li, A (A represents one element or acombination of two or more elements selected from the group consistingof Ti, Zr, Ta, Nb, Zn, W, and Al), and O; a crystallite size of thepositive electrode active substance is 80 to 490 nm; and a ratio(crystallite size/average primary particle diameter) of the crystallitesize relative to an average primary particle diameter of the positiveelectrode active substance, which is calculated from a scanning-typeelectron microscope (SEM) image obtained by a SEM, is 0.01 to 0.32;

wherein, with regard to a D50, a mode diameter, and a D10 of thepositive electrode active substance, the D50 is 0.5 to 9 μm, apercentage of a ratio of the absolute value of the difference betweenthe mode diameter and the D50 relative to the mode diameter ((|modediameter−D50|/mode diameter)×100) is 0 to 25%, a percentage of a ratioof the absolute value of the difference between the mode diameter andthe D10 relative to the mode diameter ((|mode diameter−D10|/modediameter)×100) is 20 to 58%; and wherein a ratio (average primaryparticle diameter/D50) of the average primary particle diameter of thepositive electrode active substance relative to the D50 is 0.20 to 0.99.

Effect of the Invention

The positive electrode active substance for an all solid-state lithiumsecondary battery proposed by the present invention is able to achieveboth lithium ion conductivity improvement and resistance suppression; toreduce the contact resistance between the positive electrode activesubstance and the solid electrolyte; to maintain a high operatingvoltage during discharge; and to effectively improve the ratecharacteristics and cycle characteristics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a volume-based particle size distribution obtained bymeasuring a positive electrode active substance (sample), that is, asurface-coated spinel-type lithium manganese-containing composite oxideobtained in Example 2 using a laser diffraction scattering-type particlesize distribution measurement method.

FIG. 2 shows an observation of a halo pattern obtained by selected areaelectron diffraction in regard to the positive electrode activesubstance (sample) obtained in Example 2.

MODE(S) FOR CARRYING OUT THE INVENTION

Next, the present invention will be described based on exemplaryembodiments for carrying out the present invention. However, the presentinvention is not limited to the embodiments described below.

[Present Positive Electrode Active Substance]

The positive electrode active substance according to one example of theembodiments of the present invention is a positive electrode activesubstance to be used for an all solid-state lithium secondary batteryusing a solid electrolyte, and is a positive electrode active substance(referred to as “present positive electrode active substance”)comprising a structure in which the surface of particles (referred to as“present core particles”) composed of a spinel-type composite oxidecontaining Li, Mn, O, and two or more elements other than these iscoated with an amorphous compound (referred to as “present amorphouscompound”) containing Li, an A element (A represents one element or acombination of two or more elements selected from the group consistingof Ti, Zr, Ta, Nb, Zn, W, and Al), and O; and having an operatingpotential of 4.5 V or more at a metal Li reference potential.

Here, the “having an operating potential of 4.5 V or more at a metal Lireference potential” is meant to include a case in which the presentpositive electrode active substance need not have only an operatingpotential of 4.5 V or more as a plateau region, and has a part ofoperating potential of 4.5 V or more.

From this viewpoint, the present positive electrode active substance isnot limited to a positive electrode active substance composed only of a5 V-class positive electrode active substance having an operatingpotential of 4.5 V or more as a plateau region. For example, a positiveelectrode active substance having an operating potential of less than4.5 V as a plateau region may be contained. Specifically, it is allowedthat the present positive electrode active substance may occupy 30% bymass or more, preferably 50% by mass or more, even more preferably 80%by mass or more (including 100% by mass) of the 5 V-class positiveelectrode active substance.

<Present Core Particles>

The present core particles are particles composed of a spinel-typecomposite oxide containing Li, Mn, O, and two or more elements otherthan these.

At least one element of the above “two or more elements other thanthese” may be an element M1 selected from the group consisting of Ni,Co, and Fe, and another element may be an element M2 composed of oneelement or a combination of two or more elements selected from the groupconsisting of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr,Nb, Mo, In, Ta, W, Re, and Ce.

A preferred composition example of the present core particles mayinclude a composition that contains a spinel-type lithiummanganese-containing composite oxide having a crystal structure in whicha part of the Mn site in LiMn₂O_(4-δ) is substituted with Li, the metalelement M1, and the other metal element M2.

The metal element M1 is a substitution element mainly contributing inexhibiting an operating potential of 4.5 V or more at a metal Lireference potential, and examples thereof may include Ni, Co, and Fe.The metal element M1 may contain at least one of these elements, andparticularly preferably contain at least one element of Ni and Co.

The metal element M2 is a substitution element mainly contributing instabilizing the crystal structure to enhance the characteristics, andexamples of the substitution element that contributes to an improvementin capacity retention rate may include Na, Mg, Al, P, K, Ca, Ti, V, Cr,Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce. The metal elementM2 may contain at least one element selected from the group consistingof Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, In, Ta,W, Re, and Ce, and may also contain other metal elements.

Here, the metal element M2 contained in the structure is a differentelement species from the metal element M1.

An example of the composition of the present core particles may be acomposition containing a spinel-type lithium manganese-containingcomposite oxide represented by a formula (1):Li_(x)(M1_(y)M2_(z)Mn_(2-x-y-z))O_(4-δ). M1 and M2 in the formula (1)are as described above.

In the formula (1), the parameter “x” may be 1.00 to 1.20. Among others,the parameter “x” is preferably 1.01 or more or 1.10 or less, morepreferably 1.02 or more or 1.08 or less.

The parameter “y” that represents the content of M1 may be 0.20 to 1.20.Among others, the parameter “y” is preferably 0.30 or more or 1.10 orless, more preferably 0.35 or more or 1.05 or less.

The parameter “z” that represents the content of M2 may be 0.001 to0.400. Among others, the parameter “z” is preferably 0.002 or more or0.400 or less, more preferably 0.005 or more or 0.30 or less, even morepreferably 0.10 or more. In particular, when the parameter “z” is 0.10or more, the cycle characteristics can be more effectively enhanced.

Another example of the composition of the present core particles may bea composition containing a spinel-type lithium manganese-containingcomposite oxide represented by a formula (2):[Li_(x)(Ni_(y)M_(z)Mn_(3-x-y-z))O_(4-δ)].

In the formula (2), the parameter “x” may be 1.00 to 1.20. Among others,the parameter “x” is preferably 1.01 or more or 1.10 or less, morepreferably 1.02 or more or 1.08 or less.

In the formula (2), the parameter “y” may be 0.20 to 0.70. Among others,the parameter “y” is preferably 0.30 or more or 0.60 or less, morepreferably 0.35 or more or 0.55 or less.

In the formula (2), M is preferably one element or a combination of twoor more elements selected from the group consisting of Na, Mg, Al, P, K,Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce.

In the formula (2), the parameter “z” that represents a molar ratio of Mis preferably more than 0 and 0.5 or less, more preferably more than0.01 or 0.45 or less, even more preferably 0.05 or more or 0.40 or less,still more preferably 0.10 or more or 0.35 or less. In particular, whenthe parameter “z” is 0.10 or more, the cycle characteristics can beeffectively enhanced.

Here, the “4-δ” in each formula indicates that the present coreparticles may also contain oxygen deficiency. A part of oxygen may besubstituted with fluorine or other elements. In so doing, the parameter“δ” is preferably 0 or more or 0.2 or less, more preferably 0.1 or less,even more preferably 0.05 or less.

The present core particles may contain components other than Li, Mn, M,M1, M2, and O. In particular, the other elements may be contained if at0.5% by weight or less respectively. This is conceivably because theamount in such degrees scarcely affect the performance of the presentcore particles.

In addition, the present core particles may contain B. In so doing, acomposite oxide phase containing Ni, Mn, and B may be contained as astate where B is present, in addition to the spinel crystal phase.Examples of the composite oxide phase containing Ni, Mn, and B mayinclude a crystal phase of Ni₅MnO₄(BO₃)₂.

Whether the crystal phase of Ni₅MnO₄(BO₃)₂ is contained can be confirmedby collating a diffraction pattern obtained by X-ray diffraction (XRD)with PDF (Powder Diffraction File) No. “01-079-1029”.

The composite oxide containing Ni, Mn and B is inferred to be present onthe surface or at the grain boundary of the present core particles.

In regard to the content of the composite oxide phase containing Ni, Mn,and B, the composite oxide phase is preferably contained such that thecontent of the B element in the present core particles is 0.02 to 0.80%by mass, more preferably 0.05% by mass or more or 0.60% by mass or less,even more preferably 0.30% by mass or less, particularly preferably0.25% by mass or less.

When the content of the B element is 0.02% by mass or more, thedischarge capacity at high temperature (for example, 45° C.) can bemaintained, and when the content of the B element is 0.80% by mass orless, the rate characteristics can be maintained, which is preferable.

Here, whether or not a composite oxide constituting the present coreparticles has a spinel-type structure can be confirmed according towhether or not, for example, the range of Rwp or S which represents thedegree of coincidence of an observed intensity with a calculatedintensity is Rwp<10 or S<2.5 when fitting to a crystal structure modelof a cubic crystal of a space group Fd-3m (Origin Choice 2).

The primary particles of the present core particles are preferablycomposed of a polycrystal rather than a single crystal.

Here, the single crystal means a state where the primary particles areconstituted by one crystallite, and the polycrystal means a state wherea plurality of crystallites are present in the primary particles.

Whether or not the present core particles are composed of a polycrystalcan be confirmed by observing a cross section of the primary particlesby electron back scattering diffraction (EBSD). When the present coreparticles are composed of a polycrystal, it can be confirmed thatcrystals having a plurality of orientations are present in the primaryparticles.

<Present Amorphous Compound>

As described above, the present positive electrode active substance hasa structure in which the surface of the present core particles is coatedwith the present amorphous compound containing Li, an A element (Arepresents one element or a combination of two or more elements selectedfrom the group consisting of Ti, Zr, Ta, Nb, Zn, W, and Al), and O.

The present amorphous compound may be present as particles, may bepresent as aggregated particles formed by aggregating particles, or maybe present by forming a layer, on the surface of the present coreparticles.

Here, the “present by forming a layer” means a state in which thepresent amorphous compound is present with a thickness.

In addition, when almost the whole surface of the present core particlesis coated with the present amorphous compound, there may be areas wherethe present amorphous compound is not present on a part of area orseveral partial areas of the surface of the present core particles.Here, whether the surface of the present core particles is coated withthe present amorphous compound can be confirmed by observing the surfaceof the present core particles by using, for example, an electronmicroscope. Further, the thickness of the present amorphous compound tobe coated on the surface of the present core particles may not beuniform.

The present amorphous compound is preferably amorphous. By beingamorphous, the present amorphous compound is present as a buffer layerbetween the positive electrode active substance and the solidelectrolyte, and thus the reaction resistance can be reduced.

Whether a compound to be coated on the surface of the present coreparticles is crystalline or amorphous can be judged by confirmingwhether a halo pattern can be obtained by selected area electrondiffraction. Here, the halo pattern means a low-angle and broaddiffraction pattern having no clear diffraction peak.

The present amorphous compound preferably contains Li, an A element (Arepresents one or more elements selected from the group consisting ofTi, Zr, Ta, Nb, Zn, W, and Al), and O.

When the A element is at least one element of Ta and Nb, the compositionof the present amorphous compound can be represented by, for example,Li_(x)AO_(y). Typically, LiAO₃, that is, the composition when x=1 andy=3 can be assumed. However, because the compound is an amorphouscompound, the parameters x and y in the formula can take arbitraryvalues in ranges according to valences of the elements. Among others, acomposition (1<x) containing Li in excess of 1 mol relative to 1 mol ofthe A element is more preferred.

Examples of the method for satisfying 1<x in the amorphous compound ofLi_(x)AO_(y) may include a method in which the blending amount of thelithium raw material with respect to the A element raw material isadjusted such that the amount of Li becomes excessive as compared with acomposition assumed to be generated of lithium carbonate, for example, astoichiometric composition ratio of LiAO₃.

However, when an excessive amount of Li is merely added, lithiumcarbonate caused by the excessive amount of Li is generated on thesurface of the present positive electrode active substance to becomeresistance, and instead, the rate characteristics and the cyclecharacteristics tend to deteriorate. Thus, by taking this point, thatis, the generation of lithium carbonate into consideration, it ispreferable to adjust the blending amount of the A element raw materialand the blending amount of the lithium raw material such that theamorphous compound has a predetermined composition.

<Present Positive Electrode Active Substance>

The present positive electrode active substance preferably has thefollowing features.

(Crystallinity)

The primary particles of the present positive electrode active substanceare preferably composed of a polycrystal rather than a single crystal.More specifically, it is preferable that the amorphous compound which isamorphous is present on the surface of the core particles which arepolycrystalline.

Whether or not the primary particles of the present positive electrodeactive substance are not composed of a single crystal, that is, theprimary particles thereof are composed of a polycrystal can be judged byconfirming whether a ratio of the crystallite size to the averageprimary particle diameter (crystallite size/average primary particlediameter) is nearly 0, specifically within a range of higher than 0 andlower than 1. The ratio which is nearly 0 indicates that a large numberof crystallites are contained in the primary particles. However, thepresent invention is not limited to this judging method.

Here, the “primary particles” as used in the present invention meansparticles of the smallest unit that are surrounded by grain boundarieswhen observed with a SEM (scanning electron microscope, for example, amagnification of 500 to 5,000 times).

Further, the average primary particle diameter can be determined byobserving with a SEM (scanning electron microscope, for example, amagnification of 500 to 5,000 times), selecting arbitrary 30 primaryparticles, calculating particle diameters of the selected primaryparticles using an image analysis software, and averaging the primaryparticle diameters of the 30 particles.

On the other hand, the “secondary particles” as used in the presentinvention means particles in which plural primary particles areaggregated so as to share portions of the outer peripheries (grainboundaries) of the respective particles, and are segregated from otherparticles.

The D50 according to the volume-based particle size distribution, whichcan be obtained via measurements by a laser diffraction scattering-typeparticle size distribution measurement method, has a meaning as asubstitute value of the average diameter of particles including theseprimary particles and secondary particles.

In addition, the “crystallite” means a largest aggregation which can beregarded as a single crystal, and can be determined by XRD measurementand Rietveld analysis.

(Mode Diameter)

A mode diameter of the present positive electrode active substance, thatis, a mode diameter according to a measurement of a volume-basedparticle size distribution obtained via measurements by a laserdiffraction scattering-type particle size distribution measurementmethod is preferably 0.4 to 11 μm.

In regard to the present positive electrode active substance, when themode diameter is adjusted within the above range, the resistance when Liis diffused in the secondary particles can be reduced, and as a result,the operating voltage during discharge can be maintained high.

From such a viewpoint, the mode diameter of the present positiveelectrode active substance is preferably 0.4 to 11 μm. Among others, itis more preferably 1 μm or more or 10 μm or less, even more preferably 2μm or more or 9 μm or less, still more preferably less than 8 μm.

(D50)

A D50 of the present positive electrode active substance, that is, a D50according to a measurement of a volume-based particle size distributionobtained via measurements by a laser diffraction scattering-typeparticle size distribution measurement method is preferably 0.5 to 9 μm.

In regard to the present positive electrode active substance, when theD50 is adjusted within the above range, the resistance when Li isdiffused in the secondary particles can be reduced, and as a result, theoperating voltage during discharge can be maintained high.

From such a viewpoint, the D50 of the present positive electrode activesubstance is preferably 0.5 to 9 μm. Among others, it is more preferably0.6 μm or more or 8 μm or less, even more preferably more than 1 μm orless than 8 μm, still more preferably more than 2 μm or less than 7 μm.

(|Mode Diameter−D50|/Mode Diameter)

In regard to the present positive electrode active substance, apercentage of a ratio of the absolute value of the difference betweenthe mode diameter and the D50 relative to the mode diameter ((|modediameter−D50|/mode diameter)×100) is preferably 0 to 25%.

The case where the percentage of the ratio of the absolute value of thedifference between the mode diameter and the D50 relative to the modediameter ((|mode diameter−D50|/mode diameter)×100) is 25% or lessindicates that the particle size distribution shows a single-peakedpattern, that is, a distribution having no plural peaks, and moreover, anormal distribution or a distribution similar to it.

From such a viewpoint, in regard to the present positive electrodeactive substance, the percentage of the ratio of the absolute value ofthe difference between the mode diameter and the D50 relative to themode diameter ((|mode diameter−D50|/mode diameter)×100) is preferably 0to 25%. Among others, it is more preferably more than 0% or less than20%, even more preferably more than 0.01% or less than 17%, still morepreferably more than 0.05% or less than 15%, particularly preferablymore than 0.1% or 10% or less.

(D10)

A D10 of the present positive electrode active substance, that is, a D10according to a measurement of a volume-based particle size distributionobtained via measurements by a laser diffraction scattering-typeparticle size distribution measurement method is preferably 0.2 to 4.0μm.

In regard to the present positive electrode active substance, when theD10 is adjusted within the above range, the cycle characteristics can beimproved.

From such a viewpoint, the D10 of the present positive electrode activesubstance is preferably 0.2 to 4.0 μm. Among others, it is morepreferably 0.25 μm or more or less than 4.0 μm, even more preferably 0.3μm or more or less than 3.5 μm.

(|Mode Diameter−D10|/Mode Diameter)

In regard to the present positive electrode active substance, apercentage of a ratio of the absolute value of the difference betweenthe mode diameter and the D10 relative to the mode diameter ((|modediameter−D10|/mode diameter)×100) is preferably 20 to 58%.

The case where the percentage of the ratio of the absolute value of thedifference between the mode diameter and the D10 relative to the modediameter ((|mode diameter−D10|/mode diameter)×100) is 20 to 58%indicates that the width of the distribution from the mode diameter ofthe present positive electrode active substance to the D10 thereof isnarrow.

In addition, by adjusting the percentage of the ratio of the absolutevalue of the difference between the mode diameter and the D50 relativeto the mode diameter ((|mode diameter−D50|/mode diameter)×100) to theabove range, or by adjusting the percentage of the ratio of the absolutevalue of the difference between the mode diameter and the D10 relativeto the mode diameter ((|mode diameter−D10|/mode diameter)×100) to theabove range, the particle size distribution becomes a distributionsimilar to a normal distribution and having a narrow peak. In otherwords, the sizes of the primary particles and the secondary particlescan be uniformized.

This indicates that a ratio of a fine powder region in the wholeparticle size distribution can be reduced. Since a fine powder affectsnegatively to the cycle characteristics, by reducing a ratio occupied bythe fine powder, the cycle characteristics can be improved.

From such a viewpoint, in regard to the present positive electrodeactive substance, the percentage of the ratio of the absolute value ofthe difference between the mode diameter and the D10 relative to themode diameter ((|mode diameter−D10|/mode diameter)×100) is preferably 20to 58%. Among others, it is more preferably more than 22% or less than56%, even more preferably more than 25% or less than 52%, still morepreferably more than 30% or less than 50%, particularly preferably morethan 35% or 47% or less.

(Dmin)

A Dmin of the present positive electrode active substance, that is, aDmin according to a measurement of a volume-based particle sizedistribution obtained via measurements by a laser diffractionscattering-type particle size distribution measurement method ispreferably 0.1 to 2.0 μm.

In regard to the present positive electrode active substance, when theDmin is adjusted within the above range, the cycle characteristics canbe enhanced.

From such a viewpoint, the Dmin of the present positive electrode activesubstance is preferably 0.1 to 2.0 μm. Among others, it is morepreferably 0.15 μm or more or less than 2.0 μm, even more preferably 0.2μm or more or less than 1.9 μm, still more preferably more than 0.6 μmor less than 1.8 μm.

In order to adjust the particle size distribution of the secondaryparticles of the present positive electrode active substance asdescribed above, for example, the particles may be calcined andpulverized, and may be subjected to a heat treatment after thepulverization. However, the present invention is not limited to such amethod.

(Average Primary Particle Diameter)

An average primary particle diameter of the present positive electrodeactive substance, that is, an average primary particle diametercalculated from a SEM image is preferably 0.3 to 5.0 μm.

In regard to the present positive electrode active substance, both therate characteristics and the cycle characteristics can be improved byadjusting the average primary particle diameter within the above range.

From such a viewpoint, the average primary particle diameter of thepresent positive electrode active substance is preferably 0.3 to 5.0 μm.Among others, it is more preferably more than 0.5 μm or less than 4.0μm, even more preferably more than 0.7 μm or less than 3.5 μm, stillmore preferably more than 0.9 μm or less than 3.0 μm.

(Average Primary Particle Diameter/D50)

In regard to the present positive electrode active substance, a ratio(average primary particle diameter/D50) of the average primary particlediameter relative to the D50 is preferably 0.20 to 0.99.

By specifying the ratio of average primary particle diameter/D50 withinthe above range, the dispersibility of the primary particles can beenhanced. Thus, each and every primary particle can be sufficientlybrought into contact with a solid electrolyte as compared to the casewhere the secondary particles occupies more than a half of the particlesize distribution. Accordingly, a reaction area of Li with the particlesis increased, and a resistance on the interface of the primary particlesin the secondary particles can be decreased, so that the operatingvoltage during discharge can be maintained high.

From such a viewpoint, the ratio of average primary particlediameter/D50 of the present positive electrode active substance ispreferably 0.20 to 0.99. Among others, it is more preferably 0.21 ormore or 0.98 or less, even more preferably 0.22 or more or 0.97 or less.

In order to adjust the average primary particle diameter of the presentpositive electrode active substance as described above, it is preferableto produce the present positive electrode active substance by adjustingthe calcination temperature, or adding a material which enhances thereactivity in calcination, such as a boron compound or a fluorinecompound, followed by calcining. However, the present invention is notlimited to the method.

(Crystallite Size)

In regard to the present positive electrode active substance, acrystallite size is preferably 80 to 490 nm.

By specifying the crystallite size within the above range, the ionconductivity in the crystallite can be enhanced, and thus the resistancecan be reduced. In addition, polarization during the cycle can besuppressed by reducing the resistance, and the discharge capacity can besuppressed from being gradually lowered by repetition of charging anddischarging at high temperature.

From such a viewpoint, the crystallite size of the present positiveelectrode active substance is preferably 80 to 490 nm. Among others, itis more preferably 81 nm or more or 350 nm or less, even more preferably82 nm or more or 250 nm or less, still more preferably more than 100 nmor less than 200 nm.

Here, the “crystallite” means a largest aggregation which can beregarded as a single crystal, and can be determined by XRD measurementand Rietveld analysis.

(Crystallite Size/Average Primary Particle Diameter)

In the present positive electrode active substance, a ratio (crystallitesize/average primary particle diameter) of the average primary particlediameter relative to the crystallite size is preferably 0.01 to 0.32.

As described above, since the present positive electrode activesubstance is composed of a polycrystal, the ratio of crystallitesize/average primary particle diameter becomes less than 1, and when theratio is within the above range, the dispersibility of the primaryparticles in the powder becomes good, a contact area between the primaryparticles and a solid electrolyte is increased, a resistance on theinterface of the primary particles in the secondary particles can bedecreased, and the operating voltage during discharge can be maintainedhigh.

From such a viewpoint, the ratio of crystallite size/average primaryparticle diameter in the present positive electrode active substance ispreferably 0.01 to 0.32. Among others, it is more preferably more than0.02 or less than 0.22, even more preferably more than 0.04 or less than0.15.

In regard to the present positive electrode active substance, in orderto adjust the crystallite size to the above range, it is preferable toadjust a calcination temperature, a calcination time, a supporting agentwhich enhances reactivity, a calcination atmosphere, a raw materialspecies, and the like. However, the present invention is not limited tothese methods.

(Strain)

In regard to the present positive electrode active substance, in anX-ray diffraction pattern measured by a powder X-ray diffractometer(XRD), a value of a strain obtained by Rietveld analysis is preferably0.00 to 0.35.

When the strain is small to this extent, the framework of thespinel-type lithium transition metal oxide is sufficiently rigid. Thus,when used as a positive electrode active substance of a lithiumsecondary battery, the operating voltage during discharge can bemaintained high, and the cycle characteristics can be further enhanced.

From such a viewpoint, the strain of the present positive electrodeactive substance is preferably 0.00 to 0.35. Among others, it is morepreferably less than 0.30, even more preferably less than 0.25, stillmore preferably less than 0.20, furthermore preferably less than 0.15.

In order to adjust the strain of the present positive electrode activesubstance to the above range, a heat treatment may be performed underpreferred conditions. However, the present invention is not limited tothe method.

(Specific Surface Area)

From the viewpoint of suppressing side reactions, a specific surfacearea of the present positive electrode active substance is preferably0.4 to 6.0 m²/g. Among others, it is more preferably 0.5 m²/g or more or5.0 m²/g or less, even more preferably 4.5 m²/g or less, still morepreferably 4.0 m²/g or less.

(Surface Composition)

In the present positive electrode active substance having a structure inwhich the surface of the present core particles is coated with thepresent amorphous compound, by controlling a ratio between Li and the Aelement in the present positive electrode active substance surfacewithin a predetermined range, both the lithium ion conductivityimprovement and the resistance suppression can be achieved. Also, byreducing the contact resistance between the positive electrode activesubstance and the solid electrolyte, the operating voltage duringdischarge can be maintained high, and the rate characteristics and thecycle characteristics can be effectively improved.

That is, the molar ratio (Li/A) of the Li content relative to the Aelement content in the surface of the present positive electrode activesubstance (particles), as obtained by X-ray photoelectron spectroscopy(XPS), is preferably 0.5 to 3.5. Among others, it is more preferablymore than 0.7 or 3.4 or less, even more preferably more than 1.0 or lessthan 3.0, still more preferably more than 1.1 or less than 2.5,furthermore preferably more than 1.2 or less than 2.1.

Here, the molar ratio (Li/A) is a value also including Li derived fromlithium carbonate.

In order to control the ratio between Li and the A element in thesurface of the present positive electrode active substance within therange, it is preferable to adjust the blending amount of the A elementraw material and the blending amount of the lithium raw material suchthat the molar ratio (Li/A) falls within the range while considering theLi amount derived from lithium carbonate to be generated on the presentpositive electrode active substance surface, as described above. Bydoing so, the rate characteristics and the cycle characteristics can beremarkably improved.

(Amount of Carbonate Ions: Amount of CO₃ ²⁻)

When the amount of carbonates (such as lithium carbonate and sodiumcarbonate) present on the surface of the positive electrode activesubstance is large, it may become a resistance to lower the lithium ionconductivity. Thus, the amount of carbonate ions considered to bederived from the carbonates, that is, the amount of CO₃ ²⁻ is preferablyless than 2.5 wt %, more preferably less than 1.5 wt %, even morepreferably less than 1.0 wt %, still more preferably less than 0.6 wt %,relative to the total amount of the present positive electrode activesubstance.

In order to reduce the amount of carbonate ions present on the surfaceof the present positive electrode active substance, for example,calcining under an atmosphere not containing carbon dioxide, such as anoxygen atmosphere, is preferred, and hydrolyzing while irradiatingultrasonic waves is further preferred.

[Method for Producing Present Positive Electrode Active Substance]

The present positive electrode active substance can be produced bysubjecting the present core particles to a surface coating treatment insuch a manner that, for example, the present core particles are added toa mixed solution in which a lithium raw material and an A element rawmaterial are dissolved in a solvent, and the resulting mixture is thendried and calcined under predetermined conditions. However, such aproduction method is a preferred example, and the present invention isnot limited to such a production method. The present positive electrodeactive substance can also be produced by, for example, a tumblingfluidized coating method (sol-gel method), a mechano-fusion method, aCVD method, a PVD method, or the like by adjusting the conditions.

<Method for Producing Present Core Particles>

As an example of the method for producing the present core particles, aproduction method including a raw material mixing step, a wetpulverization step, a granulation step, a calcination step, a heattreatment step, washing and drying steps, and a pulverization step, canbe cited. However, such a production method is a preferred example, andthe present invention is not limited to such a production method.

(Raw Material)

Here, raw materials for producing a substance containing a spinel-typelithium manganese-containing composite oxide represented by a formula(1): [Li_(x)(M1_(y)M2_(z)Mn_(2-x-y-z))O_(4-δ)] or a formula (2):[Li_(x)(Ni_(y)M_(z)Mn_(2-x-y-z))O_(4-δ)] will be described. However,since the present positive electrode active substance, which is theproduction object of the present invention, is not limited to thesubstances represented by the formulae (1) and (2), the raw materialscan be appropriately changed.

Examples of the raw materials for producing a spinel-type lithiummanganese-containing composite oxide represented by the formula (1):[Li_(x)(M1_(y)M2_(z)Mn_(2-x-y-z))O_(4-δ)] or the formula (2):[Li_(x)(Ni_(y)M_(z)Mn_(2-x-y-z))O_(4-δ)] may include lithium rawmaterials, nickel raw materials, manganese raw materials, M element rawmaterials, M1 element raw materials, M2 element raw materials, and otherraw materials such as boron raw materials.

Examples of the lithium raw materials may include lithium hydroxide(LiOH, LiOH.H₂O), lithium carbonate (Li₂CO₃), lithium nitrate (LiNO₃),lithium oxide (Li₂O), and besides, fatty acid lithium and lithiumhalides.

Examples of the manganese raw materials may include manganese carbonate,manganese nitrate, manganese chloride, manganese dioxide, dimanganesetrioxide, and trimanganese tetroxide. Among others, manganese carbonateand manganese dioxide are preferable. Among others, electrolyticmanganese dioxide that is obtained by an electrolytic method isparticularly preferable.

Examples of the M1 element raw materials, the M2 element raw materials,and the M element raw materials may include carbonate, nitrate,chloride, oxyhydroxide salt, hydroxide, and oxide of the M element.

In addition, a boron compound may be blended into the raw materials.

The boron compound may be a compound containing boron (B element), andfor example, it is preferable to use boric acid or a lithium borate. Asthe lithium borate, various forms thereof, for example, lithiummetaborate (LiBO₂), lithium tetraborate (Li₂B₄O₇), lithium pentaborate(LiB₅O₈), and lithium perborate (Li₂B₂O₅) can be used.

When such a boron compound is blended, the composite oxide phasecontaining Ni, Mn, and B, for example, a crystal phase of Ni₅MnO₄(BO₃)₂may be generated in addition to the crystal phase of the present coreparticles.

(Raw Material Mixing Step)

The method for mixing the raw materials is not especially limited aslong as the raw materials can be uniformly mixed. For example, therespective raw materials may be added simultaneously or in anappropriate order, and may be stirred and mixed in a wet mode or a drymode, using a known mixing machine such as a mixer, to serve as a rawmaterial mixed powder. When an element that is not easily substitutable,for example, aluminum, is added, it is preferable to employ wet mixing.

As the dry mixing, for example, a mixing method using a precision mixingmachine which rotates the raw material mixed powder at a high speed canbe exemplified.

Meanwhile, as the wet mixing, a method for adding the raw material mixedpowder to a liquid medium such as water or a dispersant, and performingwet mixing to obtain a slurry, can be cited.

(Wet Pulverization Step)

In the wet pulverization step, the raw materials may be pulverized inthe presence of a liquid medium such as water. The wet pulverization maybe performed before mixing the raw materials, or may also be performedafter mixing the raw materials.

In the case of performing the wet pulverization after mixing the rawmaterials, the raw material mixed powder is added to a liquid mediumsuch as water or a dispersant, and is wet mixed to obtain a slurry asdescribed above; and then the obtained slurry may be pulverized using awet-type pulverizer. At this time, it is particularly preferable topulverize the slurry to submicron order. By granulating and calciningthe obtained slurry after pulverizing to submicron order, the uniformityof the respective particles before the calcination reaction can beincreased, and the reactivity can be enhanced.

Meanwhile, in the case of performing the wet pulverization before mixingthe raw materials, the respective raw materials may be wet pulverizedrespectively and mixed. Thereafter, the resulting materials may befurther wet pulverized as necessary.

In the case of pulverizing the respective raw materials respectively, inorder to enhance the homogeneity in raw material mixing, it ispreferable to pulverize a raw material having a large Dmax in advancebefore mixing the raw materials. For example, it is preferable that onlya nickel compound, or a nickel compound and a manganese compound asnecessary are pulverized and classified to adjust the maximum particlediameters (Dmax) of the nickel compound and the manganese compound so asto be 10 μm or less, more preferably 5 μm or less, even more preferably4 μm or less.

(Granulation Step)

It is preferable that the raw materials mixed as described above arecalcined after being granulated to a predetermined size as necessary.However, the granulation may not be necessarily performed.

The granulation method may be a wet-type method or a dry-type method aslong as various raw materials that are pulverized in the previous stepare dispersed in the granulated particles, and may be an extrusiongranulation method, a rolling granulation method, a fluidized bedgranulation method, a mixing granulation method, a spray dryinggranulation method, a pressure molding granulation method, or a flakegranulation method using a roll or the like. However, in the case ofperforming the wet-type granulation, sufficient drying before thecalcination is needed.

The drying may be performed by known drying methods such as a spraythermal drying method, a hot-air drying method, a vacuum drying method,and a freeze-drying method, and among others, a spray thermal dryingmethod is preferred. The spray thermal drying method is preferablyperformed using a thermal spray drying machine (spray dryer). When thegranulation is performed using the thermal spray drying machine (spraydryer), a particle size distribution can be sharper, and a configurationof secondary particles can be prepared so as to include aggregatedparticles (secondary particles) that are aggregated in a round shape.

(Calcination Step)

The calcination is preferably performed in a calcining furnace under anair atmosphere, an atmosphere whose oxygen partial pressure is adjusted,a carbon dioxide gas-containing atmosphere, or other atmospheres, so asto maintain a temperature of higher than 750° C. and 1,000° C. or less,preferably 800 to 1,000° C. (meaning the temperature when a thermocoupleis brought into contact with a calcination product in a calciningfurnace) for 0.5 to 300 hours. In so doing, it is preferable to selectcalcining conditions in which transition metals are dissolved at anatomic level to form a single phase.

When the primary particles are small, there is a possibility that fineparticles that cause deterioration of the cycle characteristics areeasily generated. Thus, the calcination temperature is preferably higherthan 750° C., more preferably 800° C. or more, even more preferably 840°C. or more.

However, when the calcination temperature is too high, there is apossibility that oxygen deficiency is increased and the strain cannot berecovered even by the heat treatment. Therefore, it is preferable tocalcine at a temperature of 1,000° C. or less, more preferably 980° C.or less.

Here, the calcination temperature means a temperature of a calcinedproduct measured by bringing a thermocouple into contact with thecalcined product inside a calcination furnace.

The calcination time, that is, the time for maintaining the calcinationtemperature may vary with the calcination temperature, but it may be 0.5to 100 hours.

The kind of the calcination furnace is not particularly limited. Thecalcination can be performed by using, for example, a rotary kiln, astationary furnace, or other calcination furnaces.

Meanwhile, in the case of coexisting materials which enhance thereactivity in calcination, such as a boron compound and a fluorinecompound, the specific surface area can be lowered even at lowtemperature. In such a case, it is preferable to calcine at acalcination temperature of higher than 750° C., more preferably 800° C.or more, even more preferably 820° C. or more. However, when thecalcination temperature is too high, there is a possibility that oxygendeficiency is increased and the strain cannot be recovered even by theheat treatment. Therefore, it is preferable to calcine at a temperatureof 980° C. or less, more preferably 960° C. or less.

On the other hand, when the materials which enhance the reactivity incalcination as described above are not coexisted, it is preferable tocalcine at a temperature of higher than 800° C., more preferably 820° C.or more, even more preferably 840° C. or more. However, when thecalcination temperature is too high, there is a possibility that oxygendeficiency is increased and the strain cannot be recovered even by theheat treatment. Therefore, it is preferable to calcine at a temperatureof 1,000° C. or less, more preferably 980° C. or less.

After the calcination, it is preferable to perform a crushing asnecessary. By crushing a sintered mass or the like after calcination,oxygen can be easily incorporated into powder, and then it is possibleto suppress oxygen deficiency and to decrease strain in a heat treatmentstep that will be described later. In the present step, the crushing ispreferably performed so as not to crush the secondary particles.

(Heat Treatment Step)

The heat treatment is preferably performed under an air atmosphere, anatmosphere whose oxygen partial pressure is adjusted, or otheratmospheres, in an environment of 500 to 800° C., preferably 700° C. ormore or 800° C. or less for 0.5 to 300 hours so as to easily incorporateoxygen into the crystal structure. At this time, when the temperature islower than 700° C., the effect of the heat treatment is not easilyobtained, and there is a risk that oxygen may not be incorporated. Inaddition, when the heat treatment is performed at a temperature higherthan 800° C., desorption of oxygen begins, and the effect intended bythe present invention cannot be obtained.

In the heat treatment, the heat treatment atmosphere may be set to anatmosphere where the overall pressure of the treatment atmosphere is apressure higher than air pressure (0.1 MPa), for example, more than 0.19MPa, preferably 0.20 MPa or more, as necessary.

However, when the overall pressure of the treatment atmosphere is toohigh, there is a possibility that the production becomes unstable due toa problem on strength of the pressurized furnace. Therefore, from such aviewpoint, the heat treatment is preferably performed at an atmospherepressure of 1.5 MPa or less, more preferably 1.0 MPa or less.

By performing the heat treatment in such a pressuring state, oxygen ismore easily incorporated, and thus the oxygen deficiency can be furthersuppressed.

(Crushing and Classification Steps)

After the heat treatment step, it is preferable to crush the substance,as necessary.

In so doing, the crushing is preferably performed to an extent that thesecondary particles should not be broken.

Then, it is preferable to classify the substance after crushing.

(Washing and Drying Steps)

In the washing step, it is preferable to bring an object to be treated(also referred to as “treated powder”) into contact with a polarsolvent, and to wash the powder so as to separate impurities containedin the treated powder.

For example, the treated powder and a polar solvent are mixed andstirred to obtain a slurry, and the slurry thus obtained may besubjected to solid-liquid separation by filtration or the like, so as toeliminate impurities. In so doing, the solid-liquid separation may beperformed at a subsequent step.

Here, the slurry means a state in which the treated powder is dispersedin the polar solvent.

For the polar solvent to be used for washing, water is preferably used.

The water may be tap water, but it is preferable to use ion-exchangedwater or pure water that has been passed through a filter or a wet-typemagnetic separator.

The pH of water is preferably 4 to 10, and among others, the pH is morepreferably 5 or more or 9 or less.

As for the liquid temperature at the time of washing, it has beenconfirmed that when the liquid temperature at the time of washing islow, the battery characteristics become more satisfactory. Therefore,from such a viewpoint, the liquid temperature is preferably 5° C. to 70°C. Among others, it is more preferably 60° C. or less, even morepreferably 45° C. or less. In particular, it is furthermore preferably40° C. or less. Also, it is particularly preferably 30° C. or less.

The reason why the battery characteristics become more satisfactory whenthe liquid temperature at the time of washing is low, can be consideredthat when the liquid temperature is too high, lithium in the lithiummanganese-containing composite oxide is ion-exchanged with protons ofthe ion-exchanged water, thereby the lithium is removed, which affectshigh temperature characteristics.

As for the amount of the polar solvent that is brought into contact withthe object to be treated (treated powder), it is preferable to adjustthe mass ratio (also referred to as “slurry concentration”) of thelithium manganese-containing composite oxide relative to the total ofthe lithium manganese-containing composite oxide and the polar solventto 10 to 70 wt %, more preferably 20 wt % or more or 60 wt % or less,even more preferably 30 wt % or more or 50 wt % or less. When the slurryconcentration is 10 wt % or more, impurities such as SO₄ are easilyeluted, and on the contrary, when the slurry concentration is 60 wt % orless, a washing effect adequate for the amount of the polar solvent canbe obtained.

When the object to be treated is washed, it may be introduced into awashing liquid, followed by stirred, left to stand, and then asupernatant may be removed. For example, the spinel-type lithiummanganese-containing composite oxide is introduced into a washingliquid, stirred for 20 minutes, and left to stand for 10 minutes.Thereafter, it is preferable to remove the spinel-type lithiummanganese-containing composite oxide contained in the supernatant. Byremoving the spinel-type lithium manganese-containing composite oxidecontained in the supernatant as described above, the amount of aspinel-type lithium manganese-containing composite oxide having anincomplete crystal structure that causes deterioration of the cyclecharacteristics when being constituted in a battery can be decreased.The spinel-type lithium manganese-containing composite oxide recoveredby the solid-liquid separation is preferably heated to 300° C. or moreto sufficiently remove moisture.

(Pulverization Step)

In the pulverization step, it is preferable to pulverize the objectusing an airflow-type pulverizer, a classification mechanism-equippedcollision-type pulverizer, for example, a jet mill, a classifyingrotor-equipped counter jet mill, or the like. When the pulverization isperformed using a jet mill, an aggregation of the primary particles or apart where the degree of the calcination is weak can be pulverized.However, it is not limited to a jet mill. Pulverizers such as a pin milland a planetary ball mill can also be used.

An example of the jet mill may be a classifying rotor-equipped counterjet mill. The counter jet mill is known as a pulverizer utilizing acollision of compressed gas flow. Raw materials supplied from a rawmaterial hopper to the mill are fluidized by injection air from thenozzle. In so doing, the counter jet mill is placed such that theinjection air converges to one point. Thus, the particles acceleratedduring the jet collide each other, and the particles can be finelypulverized.

The rotation speed of the classifier of the counter jet mil ispreferably 7,000 rpm or more. Among others, it is more preferably 8,000rpm or more or 18,000 rpm or less, even more preferably 9,000 rpm ormore or 18,000 rpm or less.

(Oxygen-Containing Atmosphere Heat Treatment Step After PulverizationStep)

After the pulverization step, a heat treatment may be performed in anoxygen-containing atmosphere as necessary.

By performing a heat treatment in an oxygen-containing atmosphere afterthe pulverization step, oxygen can be incorporated into the structure,and a strain caused by the pulverization can be further reduced.

In the oxygen-containing atmosphere heat treatment step after thepulverization step, it is preferable to perform a heat treatment at atemperature of higher than 500° C. and lower than 850° C. in a treatmentatmosphere in which the overall pressure in the treatment atmosphere isair pressure or higher than air pressure and the oxygen partial pressurein the atmosphere is higher than the oxygen partial pressure in airpressure.

By performing the heat treatment in an oxygen-containing atmosphere asdescribed above, oxygen is incorporated into the structure of thepresent core particles, and thus the oxygen deficiency is decreased andthe structure is stabilized. Therefore, even in the case of calcining athigh temperature or even after pulverizing as described above, thestrain in the structure can be eliminated, so that the resistance can bereduced and the cycle characteristics can be improved.

Here, the pressure atmosphere which is higher than air pressure includesa case where the pressure becomes a pressure higher than air pressure byheating an inside of sealed container and rising a temperature of gas ina certain volume for increasing the pressure.

Here, in the atmosphere having a pressure higher than air pressure, theoverall pressure of the atmosphere is preferably a pressure higher thanair pressure (0.1 MPa), for example, more than 0.19 MPa, and morepreferably 0.20 MPa or more. However, when the overall pressure of thetreatment atmosphere is too high, there is a possibility that theproduction becomes unstable due to a problem on strength of thepressurized furnace. Therefore, from such a viewpoint, the heattreatment is preferably performed at an atmosphere pressure of 1.5 MPaor less, more preferably 1.0 MPa or less. As such, by performing theheat treatment in a state of pressuring in an oxygen-containingatmosphere, oxygen is more easily incorporated, and thus the oxygendeficiency can be further suppressed. From such a viewpoint, the overallpressure in the atmosphere during the oxygen-containing atmospherepressure heat treatment is preferably controlled to higher than 0.19 MPaand 1.5 MPa or less, more preferably 0.20 MPa or more or 1.3 MPa orless, even more preferably 1.0 MPa or less.

Further, in the atmosphere having a pressure higher than air pressure,it is preferable that the oxygen partial pressure is, for example,higher than 0.19 MPa, and more preferably 0.20 MPa or more. However,when the oxygen partial pressure is too high, there is a possibilitythat the production becomes unstable due to a problem on strength of thepressurized furnace. Therefore, from such a viewpoint, the heattreatment is preferably performed under an oxygen partial pressure of1.5 MPa or less, more preferably 1.0 MPa or less.

From such a viewpoint, the oxygen partial pressure in thepost-pulverizing oxygen-containing atmosphere heat treatment step ispreferably controlled to higher than 0.19 MPa and 1.5 MPa, morepreferably 0.20 MPa or more or 1.3 MPa or less, even more preferably 1.0MPa or less.

The heat treatment temperature in the oxygen-containing atmosphere heattreatment step after the pulverization step, that is, the retentiontemperature is preferably controlled to a temperature higher than 500°C. and lower than 850° C.

When the heat treatment temperature in the present step is higher than500° C., and when the heat treatment is performed while forciblysupplying oxygen, the strain can be effectively decreased byincorporating oxygen into the crystal structure.

From such a viewpoint, the heat treatment temperature is preferablyhigher than 500° C., more preferably higher than 550° C., even morepreferably higher than 600° C., still more preferably higher than 620°C.

Meanwhile, when the heat treatment temperature is too high, there is apossibility that oxygen deficiency is increased, and the strain cannotbe recovered even by the heat treatment. Therefore, the heat treatmenttemperature is preferably lower than 850° C., more preferably lower than820° C., even more preferably lower than 800° C.

Here, the heat treatment temperature means a product temperature of thetreated object which is measured by bringing a thermocouple into contactwith the treated object in the furnace.

An example of the preferred conditions in the oxygen-containingatmosphere heat treatment step after the pulverization step may be acondition where the overall pressure in the treatment atmosphere ishigher than air pressure, the oxygen partial pressure is higher than0.19 MPa, and the oxygen-containing atmosphere pressure heat treatmentis performed at a temperature higher than 500° C. and lower than 850°C., among others, higher than 550° C. or lower than 850° C., and stillamong others, higher than 600° C. or lower than 800° C.

The temperature-rise rate when heating to the heat treatmenttemperature, that is, the retention temperature is preferably 0.1 to 20°C./min, more preferably 0.25° C./rain or more or 10° C./min or less,even more preferably 0.5° C./min or more or 5° C./rain or less.

The time for maintaining the heat treatment temperature in theoxygen-containing atmosphere heat treatment step after the pulverizationstep needs to be at least 1 minute or more. In order to incorporateoxygen into the crystal structure sufficiently, it is considered that atleast one minute is necessary. From such a viewpoint, the retention timeof the heat treatment temperature is preferably 5 minutes or more, morepreferably 10 minutes or more. Further, it is considered that when theretention time is 200 hours or less, an effect in which oxygen isincorporated into the crystal structure is sufficiently obtained.

As for the temperature-fall rate after heat treatment, it is preferableto cool slowly at a cooling rate of 10° C./min or less at least to 500°C., and it is more preferable to control the cooling rate of 0.1 to 8°C./rain, even more preferably 0.2 to 5° C./rain.

Since it is considered that the oxygen thus incorporated is stabilizedat near 500° C., it can be considered that it is preferable to coolslowly at a temperature-fall rate of 10° C./min or less at least to 500°C.

The heat treatment in the oxygen-containing atmosphere heat treatmentstep after the pulverization step as described above can be performed byheating using an apparatus such as a pressurized furnace (pressurizablepressure is 1.0 MPa) at a treatment atmosphere where the overallpressure in the treatment atmosphere is higher than air pressure and theoxygen partial pressure in the atmosphere is higher than an oxygenpartial pressure in air pressure.

(Crushing and Classification Steps)

After the oxygen-containing atmosphere heat treatment step after thepulverization step, the substance may be crushed as necessary.

In so doing, the crushing is preferably performed to an extent that theprimary particles should not be broken.

Then, it is preferable to classify the substance after crushing.

<Surface Coating Treatment>

In order to coat the surface of the present core particles thus producedwith the present amorphous compound containing Li, the A element, and O,for example, the present core particle powder may be added to a mixedsolution obtained by dissolving the lithium raw material and the Aelement raw material in a solvent, and the resulting product may bedried and calcined under a predetermined condition as described above.

More specifically, it is preferable that the lithium raw material andthe A element raw material, in both of which a ratio between the Liamount and the A element amount is adjusted within a predeterminedrange, are stirred and dissolved in a solvent, and then the present coreparticle powder is introduced therein.

Here, examples of the lithium raw material may include lithium alkoxideand lithium salt. Specifically, lithium ethoxide (C₂H₅OLi) and the likecan be used as the lithium raw material. Examples of the A element rawmaterial may include one having OH group at the terminal and one thatbecomes a hydroxide after being hydrolyzed. Specifically, pentaethoxyniobium (Nb(C₂H₅O)₅) and the like can be used as the A element rawmaterial.

The solvent is not especially limited as long as being an organicsolvent capable of dissolving the lithium raw material and the A elementraw material. For example, ethanol and the like can be cited as thesolvent. In addition, the solvent is preferably an anhydrous solvent.

In addition to the above, when a watersoluble raw material such as LiOHor Li₂CO₃ is used as the lithium raw material, or a watersoluble Aelement raw material is used, water can be used as the solvent.

Here, the ratio of the lithium raw material to the A element rawmaterial is preferably adjusted such that the molar ratio (Li/A) of Lirelative to the A element on the surface of the present positiveelectrode active substance, as obtained by XPS, is to be 0.5 to 3.5.

Further, in order to reduce the amount of lithium carbonate present onthe surface of the positive electrode active substance, the calcinationis preferably performed under, for example, an atmosphere not containingcarbon dioxide such as an oxygen atmosphere.

In addition, when the calcination temperature is 400° C. or less, thecompound that coats the surface of the present core particles can beamorphous. Thus, from such a viewpoint, the calcination temperature ispreferably higher than 200° C. and 400° C. or less. Among others, it ismore preferably higher than 250° C. or lower than 400° C., even morepreferably higher than 300° C. or 350° C. or less.

<Application of Present Positive Electrode Active Substance>

The present positive electrode active substance can be suitably utilizedas a positive electrode active substance for an all solid-state lithiumsecondary battery using a solid electrolyte after being crushed andclassified as necessary.

In so doing, the present positive electrode active substance alone maybe used as a positive electrode active substance for an all solid-statelithium secondary battery, or the present positive electrode activesubstance may be used by mixing with the other positive electrode activesubstance, for example, a positive electrode active substance composedof the present core particles or a positive electrode active substancecomposed of the other composition, such as LiCoO₂, LiNiO₂, LiMn₂O₄,LiCo_(1/3)Ni_(1/3)Mn_(1/3)O₂, LiCo_(0.5)Ni_(0.5)O₂,LiNi_(0.7)Co_(0.2)Mn_(0.1)O₂, Li(Li_(x)Mn_(2x)Co_(1-3x))O₂ (where0<x<⅓), LiFePO₄, or LiMn_(1-z)M_(z)PO₄ (where 0<z≤0.1 and M representsat least one metal element selected from the group consisting of Co, Ni,Fe, Mg, Zn, and Cu).

However, in the case of mixing with the other positive electrode activesubstance, the present positive electrode active substance is preferablymixed so as to occupy 50 wt % or more.

Examples of the shape of the all solid-state lithium secondary batterymay include a laminate-type, a cylindrical-type, and a square-type.

For example, the all solid-state lithium secondary battery can beconstituted by forming a layer composed of a solid electrolyte betweenthe positive electrode and the negative electrode, and the allsolid-state lithium secondary battery can be assembled even in a dryroom or the like.

Examples of the solid electrolyte may include a compound represented byLi_(7-x)PS_(6-x) (Halogen)_(x) (Halogen represents a group 17 element: ahalogen element). Among others, a solid electrolyte containing sulfur,for example, a solid electrolyte composed of a compound containinglithium, phosphorus, sulfur, and halogen, and having a cubicargyrodite-type crystal structure, can be cited.

Examples of the negative electrode active substance may include anegative electrode active substance containing carbon such as artificialgraphite, natural graphite, or non-graphitizing carbon (hard carbon). Inaddition, silicon or tin promising as a high capacity material can alsobe used as an active substance.

A lithium battery constituted in this manner can be used, for example,in electronic devices such as laptop computers, mobile phones, cordlesstelephone handsets, video movies, liquid crystal televisions, electricshavers, portable radios, headphone stereos, backup power supplies, andmemory cards, medical devices such as pacemakers and hearing aids, anddriving power supplies for being mounted in electric vehicles. Amongothers, the lithium battery is particularly effective as various kindsof portable computers such as mobile phones, PDAs (portable informationterminals), and laptop computers, electric vehicles (including hybridvehicles), and driving power supplies for electric power storage, whichrequire excellent cycle characteristics.

Explanation of Terms

In the case of being expressed as the term “X to Y” (X and Y arearbitrary numbers) in the present description, unless otherwise stated,the term includes the meaning of “preferably more than X” or “preferablyless than Y” along with the meaning “not less than X and not more thanY”.

Further, in the case of being expressed as the term “X or more” (X is anarbitrary number) or the term “Y or less” (Y is an arbitrary number),the term also includes the intention of being “preferably more than X”or “preferably less than Y”.

EXAMPLES

Next, the present invention will be described further based on Examplesand Comparative Example. However, the present invention is not limitedto the following Examples.

Example 1

Lithium carbonate having an average particle diameter (D50) of 7 μm,electrolytic manganese dioxide having an average particle diameter (D50)of 23 μm and a specific surface area of 40 m²/g, nickel hydroxide havingan average particle diameter (D50) of 22 μm, titanium oxide having anaverage particle diameter (D50) of 2 μm, and aluminum hydroxide havingan average particle diameter (D50) of 3 μm were weighed respectively.

A polycarboxylic acid ammonium salt aqueous solution (SN Dispersant5468, manufactured by San Nopco Ltd.) was added as a dispersant toion-exchanged water. In so doing, an amount of the dispersant that wasadded was set to 6 wt % with respect to a total amount of the Li rawmaterial, the Ni raw material, the Mn raw material, the Ti raw material,and the Al raw material, and the dispersant was sufficiently dissolvedin and mixed with the ion-exchanged water. Then, the Ni, Mn, and Al rawmaterials that had been weighed were added to the ion-exchanged water inwhich the dispersant was dissolved in advance, and the resulting mixturewas mixed and stirred, followed by pulverized using a wet-typepulverizer at 1,300 rpm for 120 minutes, thereby obtaining a pulverizedslurry having an average particle diameter (D50) of 0.60 μm or less.Next, the remaining raw materials were added to the slurry, and theresulting mixture was stirred, followed by pulverized at 1,300 rpm for120 minutes, thereby obtaining a pulverized slurry having an averageparticle diameter (D50) of 0.60 μm or less. A solid contentconcentration at this time was set to 40 wt %.

The pulverized slurry thus obtained was granulated and dried using athermal spray drying machine (Spray Dryer “RL-10”, manufactured byOhkawara Kakohki Co., Ltd.). In so doing, a twin-jet nozzle was used forspraying, and the granulation and drying was performed under conditionswhere the spray pressure was set to 0.46 MPa, the slurry supply amountwas set to 340 ml/min, and the temperature was adjusted such that anoutlet temperature of a drying tower became 100 to 110° C.

The obtained granulated powder was calcined using a stationary electricfurnace under an air atmosphere so as to maintain a temperature of 900°C. for 37 hours, and was then crushed using a crusher (Orientvertical-type pulverizing machine, manufactured by Orient PulverizingMachine Co., Ltd.).

After the crushing, the crushed powder was subjected to a heat treatment(first heat treatment) using a stationary electric furnace under an airatmosphere so as to maintain a temperature of 750° C. for 37 hours, andwas then crushed using a crusher (Orient vertical-type pulverizingmachine, manufactured by Orient Pulverizing Machine Co., Ltd.).

After the crushing, the crushed powder was introduced into a plasticbeaker (capacity of 5,000 mL) which was filled with 2,000 mL ofion-exchanged water having a pH of 6 to 7 and a temperature of 25° C.,and the content was stirred using a stirrer (propeller area of 33 cm²)at a rotation speed of 400 to 550 rpm for 20 minutes.

After stirring, the stirring was stopped, the stirrer was taken out fromthe water, and the resulting stirred product was left to stand for 10minutes. Then, the supernatant was removed by decantation, the residualwas collected as a precipitate by using a suction filtration machine(filter paper No. 131), and the precipitate thus collected was dried inan environment of 120° C. for 12 hours. Thereafter, the resultingproduct was dried for 7 hours in a state of being heated so as to havethe product temperature of 500° C.

Then, after drying, the resulting dried product was crushed using acounter jet mill (pulverizing and classifying apparatus, manufactured byHosokawa Micron Corp.) (crushing condition: rotation speed of classifierof 11,000 rpm). Thereafter, the resulting crushed product was classifiedusing a sieve having an aperture of 53 μm.

Thereafter, the resulting classified product was subjected to a heattreatment (second heat treatment) while flowing oxygen at an oxygensupply amount of 0.5 L/min in a tubular stationary furnace so as tomaintain a furnace set temperature of 725° C. for 5 hours.

The powder obtained after the second heat treatment was classified usinga sieve having an aperture of 53 μm, and the powder under the sieve wascollected to obtain a lithium manganese-containing composite oxide. Thelithium manganese-containing composite oxide was identified as aspinel-type lithium manganese-containing composite oxide by XRDmeasurement as described later. Therefore, the lithiummanganese-containing composite oxide is referred to as a spinel-typelithium manganese-containing composite oxide. The same applies to thefollowing Examples and Comparative Example.

The spinel-type lithium manganese-containing composite oxide, that is,the core particles were chemically analyzed, and the results were Li:4.1 wt %, Ni: 13.6 wt %, Mn: 41.7 wt %, Ti: 5.4 wt %, and Al: 0.01 wt %.From the cross-sectional SEM photograph of the primary particles, it wasconfirmed that the core particles were polycrystalline.

The composition when expressing by a general formula:[Li_(x)(M1_(y)M2_(z)Mn_(2-x-y-z))O_(4-δ)] (assuming δ=0) is shown inTable 1. The M1 represents Ni in the present Example, and thesubstitution element species M2 represents Ti and Al in the presentExample (the same applies to the following Examples and ComparativeExample).

Here, the temperatures in the calcination and in the heat treatment areproduct temperatures of the treated object which are measured bybringing a thermocouple into contact with the treated object in thefurnace. The same applies to the following Examples and ComparativeExample.

Then, Nb was employed as the A element, lithium ethoxide was used as thelithium raw material, and pentaethoxy niobium was used as the Nb rawmaterial.

Predetermined amounts of lithium ethoxide and pentaethoxy niobium wereweighed, and these were added to ethanol and dissolved to prepare asol-gel solution for coating. 5 g of the spinel-type lithiummanganese-containing composite oxide powder was introduced into thesol-gel solution for coating, and subjected to ultrasonic irradiationwhile being heated at 60° C. for 30 minutes using a rotary evaporator tobe hydrolyzed. Thereafter, the pressure was reduced over 30 minuteswhile maintaining 60° C. to remove the solvent. After removing thesolvent, it was left to stand at room temperature for 16 hours anddried. Next, the resulting product was subjected to a heat treatment(third heat treatment) so as to maintain 350° C. for 5 hours in an airatmosphere using a box-type small electric furnace (manufactured by KoyoThermo Systems Co., Ltd.), thereby obtaining a surface-coatedspinel-type lithium manganese-containing composite oxide powder, thatis, a positive electrode active substance (sample).

Example 2

A surface-coated spinel-type lithium manganese-containing compositeoxide powder, that is, a positive electrode active substance (sample)was obtained in the same manner as in Example 1 except that the rawmaterial ratio was changed, the Al raw material was not used, thecalcination temperature was changed to 890° C., and the amounts oflithium ethoxide and pentaethoxy niobium were changed.

Here, the spinel-type lithium manganese-containing composite oxidepowder, that is, the core particles were chemically analyzed, and theresults were Li: 4.2 wt %, Ni: 13.2 wt %, Mn: 41.6 wt %, and Ti: 5.0 wt%. From the cross-sectional SEM photograph of the primary particles, itwas confirmed that the core particles were polycrystalline.

Example 3

A surface-coated spinel-type lithium manganese-containing compositeoxide powder, that is, a positive electrode active substance (sample)was obtained in the same manner as in Example 2 except that the rawmaterial ratio was changed, the amounts of lithium ethoxide andpentaethoxy niobium were changed, and the third heat treatmenttemperature was changed to 330° C.

Here, the spinel-type lithium manganese-containing composite oxidepowder, that is, the core particles were chemically analyzed, and theresults were Li: 4.1 wt %, Ni: 13.1 wt %, Mn: 39.3 wt %, and Ti: 5.2 wt%. From the cross-sectional SEM photograph of the primary particles, itwas confirmed that the core particles were polycrystalline.

Example 4

A surface-coated spinel-type lithium manganese-containing compositeoxide powder, that is, a positive electrode active substance (sample)was obtained in the same manner as in Example 2 except that the rawmaterial ratio was changed, and the amounts of lithium ethoxide andpentaethoxy niobium were changed.

Here, the spinel-type lithium manganese-containing composite oxidepowder, that is, the core particles were chemically analyzed, and theresults were Li: 4.1 wt %, Ni: 13.3 wt %, Mn: 42.7 wt %, and Ti: 5.1 wt%. From the cross-sectional SEM photograph of the primary particles, itwas confirmed that the core particles were polycrystalline.

Example 5

A surface-coated spinel-type lithium manganese-containing compositeoxide powder, that is, a positive electrode active substance (sample)was obtained in the same manner as in Example 1 except that the rawmaterial ratio was changed, cobalt hydroxide was used as the Co rawmaterial instead of the Al raw material, the calcination temperature waschanged to 890° C., the amounts of lithium ethoxide and pentaethoxyniobium were changed, and the third heat treatment temperature waschanged to 360° C.

Here, the spinel-type lithium manganese-containing composite oxidepowder, that is, the core particles were chemically analyzed, and theresults were Li: 4.1 wt %, Ni: 13.2 wt %, Mn: 42.3 wt %, Ti: 4.9 wt %,and Co: 0.09 wt %. From the cross-sectional SEM photograph of theprimary particles, it was confirmed that the core particles werepolycrystalline.

Example 6

A surface-coated spinel-type lithium manganese-containing compositeoxide powder, that is, a positive electrode active substance (sample)was obtained in the same manner as in Example 1 except that the rawmaterial ratio was changed, magnesium oxide was used as the Mg rawmaterial instead of the Al raw material, the calcination temperature waschanged to 890° C., the amounts of lithium ethoxide and pentaethoxyniobium were changed, and the third heat treatment temperature waschanged to 370° C.

Here, the spinel-type lithium manganese-containing composite oxidepowder, that is, the core particles were chemically analyzed, and theresults were Li: 4.1 wt %, Ni: 13.2 wt %, Mn: 41.8 wt %, Ti: 5.2 wt %,and Mg: 0.002 wt %. From the cross-sectional SEM photograph of theprimary particles, it was confirmed that the core particles werepolycrystalline.

Example 7

A surface-coated spinel-type lithium manganese-containing compositeoxide powder, that is, a positive electrode active substance (sample)was obtained in the same manner as in Example 2 except that the rawmaterial ratio was changed, the calcination temperature was changed to880° C., and the amounts of lithium ethoxide and pentaethoxy niobiumwere changed.

Here, the spinel-type lithium manganese-containing composite oxidepowder, that is, the core particles were chemically analyzed, and theresults were Li: 4.1 wt %, Ni: 13.3 wt %, Mn: 39.4 wt %, and Ti: 5.2 wt%. From the cross-sectional SEM photograph of the primary particles, itwas confirmed that the core particles were polycrystalline.

Example 8

Lithium carbonate having an average particle diameter (D50) of 7 μm,electrolytic manganese dioxide having an average particle diameter (D50)of 23 μm and a specific surface area of 40 m²/g, nickel hydroxide havingan average particle diameter (D50) of 22 μm, titanium oxide having anaverage particle diameter (D50) of 2 μm, and lithium tetraborate havingan average particle diameter (D50) of 60 μm were weighed respectively.

A polycarboxylic acid ammonium salt aqueous solution (SN Dispersant5468, manufactured by San Nopco Ltd.) was added as a dispersant toion-exchanged water. In so doing, an amount of the dispersant that wasadded was set to 6 wt % with respect to a total amount of the Li rawmaterial, the Ni raw material, the Mn raw material, the Ti raw material,and the B raw material, and the dispersant was sufficiently dissolved inand mixed with the ion-exchanged water. Then, the Ni and Mn rawmaterials that had been weighed were added to the ion-exchanged water inwhich the dispersant was dissolved in advance, and the resulting mixturewas mixed and stirred, followed by pulverized using a wet-typepulverizer at 1,300 rpm for 120 minutes, thereby obtaining a pulverizedslurry having an average particle diameter (D50) of 0.60 μm or less.Next, the remaining raw materials were added to the slurry, and theresulting mixture was stirred, followed by pulverized at 1,300 rpm for120 minutes, thereby obtaining a pulverized slurry having an averageparticle diameter (D50) of 0.60 μm or less. A solid contentconcentration at this time was set to 40 wt %.

The pulverized slurry thus obtained was granulated and dried using athermal spray drying machine (Spray Dryer “RL-10”, manufactured byOhkawara Kakohki Co., Ltd.). In so doing, a twin-jet nozzle was used forspraying, and the granulation and drying was performed under conditionswhere the spray pressure was set to 0.46 MPa, the slurry supply amountwas set to 340 ml/min, and the temperature was adjusted such that anoutlet temperature of a drying tower became 100 to 110° C.

The obtained granulated powder was calcined using a stationary electricfurnace under an air atmosphere so as to maintain a temperature of 880°C. for 37 hours, and was then crushed using a crusher (Orientvertical-type pulverizing machine, manufactured by Orient PulverizingMachine Co., Ltd.).

After the crushing, the crushed powder was subjected to a heat treatment(first heat treatment) using a stationary electric furnace under an airatmosphere so as to maintain a temperature of 750° C. for 37 hours, andwas then crushed using a crusher (Orient vertical-type pulverizingmachine, manufactured by Orient Pulverizing Machine Co., Ltd.).

After the crushing, the crushed powder was introduced into a plasticbeaker (capacity of 5,000 mL) which was filled with 2,000 mL ofion-exchanged water having a pH of 6 to 7 and a temperature of 25° C.,and the content was stirred using a stirrer (propeller area of 33 cm²)at a rotation speed of 400 to 550 rpm for 20 minutes. After stirring,the stirring was stopped, the stirrer was taken out from the water, andthe resulting stirred product was left to stand for 10 minutes. Then,the supernatant was removed by decantation, the residual was collectedas a precipitate by using a suction filtration machine (filter paper No.131), and the precipitate thus collected was dried in an environment of120° C. for 12 hours. Thereafter, the resulting product was dried for 7hours in a state of being heated so as to have the product temperatureof 500° C.

Then, after drying, the resulting dried product was crushed using acounter jet mill (pulverizing and classifying apparatus, manufactured byHosokawa Micron Corp.) (crushing condition: rotation speed of classifierof 11,000 rpm). Thereafter, the resulting crushed product was classifiedusing a sieve having an aperture of 53 μm.

Thereafter, the resulting classified product was subjected to a heattreatment (second heat treatment) while flowing oxygen at an oxygensupply amount of 0.5 L/min in a tubular stationary furnace so as tomaintain a furnace set temperature of 725° C. for 5 hours.

The powder obtained after the second heat treatment was classified usinga sieve having an aperture of 53 μm, and the powder under the sieve wascollected to obtain a spinel-type lithium manganese-containing compositeoxide powder.

The spinel-type lithium manganese-containing composite oxide, that is,the core particles were chemically analyzed, and the results were Li:3.9 wt %, Ni: 14.2 wt %, Mn: 42.6 wt %, Ti: 3.6 wt %, and B: 0.1 wt %.From the cross-sectional SEM photograph of the primary particles, it wasconfirmed that the core particles were polycrystalline.

Then, Nb was employed as the A element, lithium ethoxide was used as thelithium raw material, and pentaethoxy niobium was used as the Nb rawmaterial. Predetermined amounts of lithium ethoxide and pentaethoxyniobium were weighed, and these were added to ethanol and dissolved toprepare a sol-gel solution for coating.

5 g of the spinel-type lithium manganese-containing composite oxidepowder was introduced into the sol-gel solution for coating, andsubjected to ultrasonic irradiation while being heated at 60° C. for 30minutes using a rotary evaporator to be hydrolyzed. Thereafter, thepressure was reduced over 30 minutes while maintaining 60° C. to removethe solvent. After removing the solvent, it was left to stand at roomtemperature for 16 hours and dried. Next, the resulting product wassubjected to a heat treatment (third heat treatment) so as to maintain340° C. for 5 hours in an air atmosphere using a box-type small electricfurnace (manufactured by Koyo Thermo Systems Co., Ltd.), therebyobtaining a surface-coated spinel-type lithium manganese-containingcomposite oxide powder, that is, a positive electrode active substance(sample).

Comparative Example 1

Lithium carbonate having an average particle diameter (D50) of 7 μm,electrolytic manganese dioxide having an average particle diameter (D50)of 23 μm and a specific surface area of 40 m²/g, and nickel hydroxidehaving an average particle diameter (D50) of 22 μm were weighedrespectively.

A polycarboxylic acid ammonium salt aqueous solution (SN Dispersant5468, manufactured by San Nopco Ltd.) was added as a dispersant toion-exchanged water. In so doing, an amount of the dispersant that wasadded was set to 6 wt % with respect to a total amount of the Li rawmaterial, the Ni raw material, and the Mn raw material, and thedispersant was sufficiently dissolved in and mixed with theion-exchanged water. Then, the raw materials that had been weighed wereadded to the ion-exchanged water in which the dispersant was dissolvedin advance, and the resulting mixture was mixed and stirred to prepare aslurry having a solid content concentration of 40 wt %.

The slurry was pulverized using a wet-type pulverizer at 1,300 rpm for120 minutes to have an average particle diameter (D50) of 0.60 μm orless.

The pulverized slurry thus obtained was granulated and dried using athermal spray drying machine (Spray Dryer “RL-10”, manufactured byOhkawara Kakohki Co., Ltd.). In so doing, a twin-jet nozzle was used forspraying, and the granulation and drying was performed under conditionswhere the spray pressure was set to 0.19 MPa, the slurry supply amountwas set to 350 ml/min, and the temperature was adjusted such that anoutlet temperature of a drying tower became 100 to 110° C.

The obtained granulated powder was calcined, using a stationary electricfurnace, so as to maintain a temperature of 950° C. for 37 hours underan atmosphere where the oxygen partial pressure was 0.021 MPa, and thenheat treated so as to maintain a temperature of 750° C. for 37 hoursunder an atmosphere where the oxygen partial pressure was 0.021 MPa.

The calcined powder obtained by the heat treatment was classified usinga sieve having an aperture of 53 μm, and the powder under the sieve wascollected to obtain a spinel-type lithium manganese-containing compositeoxide powder, that is, a positive electrode active substance (sample).

The spinel-type lithium manganese-containing composite oxide powder thusobtained was chemically analyzed, and the results were Li: 3.9 wt %, Ni:16.0 wt %, and Mn: 43.0 wt %.

<Method for Measuring Various Physical Property Values>

Various physical property values of the spinel-type lithiummanganese-containing composite oxide, that is, the positive electrodeactive substance (sample) obtained in each of Examples and ComparativeExample were measured as follows.

(Chemical Analysis)

As for the spinel-type lithium manganese-containing composite oxide,that is, the positive electrode active substance (sample) obtained ineach of Examples and Comparative Example, the content of the respectiveelements was measured by inductively coupled plasma (ICP) emissionspectroscopy.

(Mode Diameter, D50, D10, and Dmin)

As for the sample obtained in each of Examples and Comparative Example,the sample (powder) was introduced into a watersoluble solvent using anautomatic sample feeder for laser diffraction particle diameterdistribution measuring apparatus (“Microtorac SDC”, manufactured byMicrotoracBEL Corp.), and the sample was irradiated with ultrasonicwaves of 40 W for 360 seconds at a flow rate of 40% more than once.Subsequently, the particle size distribution was measured using a laserdiffraction particle size distribution measuring apparatus “MT3000II”manufactured by MicrotoracBEL Corp., and values of mode diameter, D50,D10, and Dmin were measured from a chart of the volume-based particlesize distribution thus obtained.

The number of irradiation times of ultrasonic waves was a number oftimes until a change rate of D50 before and after the ultrasonic wavesirradiation became 8% or less.

Here, at the time of measurement, the watersoluble solvent was filteredthrough a filter having a pore size of 60 μm, and the average valueobtained by performing two measurements under the conditions of asolvent refractive index of 1.33, penetration for the particlepenetrability conditions, a particle refractive index of 2.46, anon-spherical shape, a measurement range of 0.133 to 704.0 μm, and ameasurement time of 30 seconds, was defined as respective values.

(Average Primary Particle Diameter)

An average primary particle diameter of the spinel-type lithiummanganese-containing composite oxide, that is, the positive electrodeactive substance (sample) obtained in each of Examples and ComparativeExample was measured as follows.

The sample (powder) was observed using a SEM (scanning electronmicroscope) at a magnification of 1,000 times, and particles having asize corresponding to D50 were selected. Next, the sample (powder) wasphotographed by changing a magnification from 2,000 to 10,000 times inaccordance with D50. An image which is suitable for obtaining an averageprimary particle diameter by using image analysis software describedlater can be photographed by setting a photographing magnification to,for example, 10,000 times when the D50 is about 7 μm, 5,000 times whenthe D50 is about 15 μm, and 2,000 times when the D50 is about 22 μm.

With the photographed image, the average primary particle diameter ofthe selected particles was obtained using image analysis software(MAC-VIEW ver. 4, manufactured by Mountech Co., Ltd.). Here, the averageprimary particle diameter means a 50% accumulated particle diameter in avolume distribution (Heywood diameter: equivalent circle diameter).

In order to calculate the average primary particle diameter, it ispreferable to measure 30 pieces or more of the primary particles and tocalculate the average value. When the number of the measurementparticles was insufficient, the measurement was performed byadditionally selecting the particles having a size equivalent to D50 andphotographing so that the number of the primary particles became 30pieces or more in total.

(Identification of Crystal Structure)

As for the spinel-type lithium manganese-containing composite oxideobtained in each of Examples and Comparative Example, the crystalstructure was identified using an XRD apparatus as follows.

The XRD measurement was performed under the following measurementconditions 1 using an XRD measurement apparatus (apparatus name “UltimaIV”, manufactured by Rigaku Corp.) to obtain an XRD pattern. Theobtained XRD pattern was analyzed using an integrated X-ray powderdiffraction software PDXL (manufactured by Rigaku Corp.) to determine acrystal phase information.

Here, on the assumption that, in the crystal phase information, thecrystal structure is attributed to a cubic crystal of a space groupFd-3m (Origin Choice 2), and the 8a site is occupied by Li, the 16d siteis occupied by Mn, the M1 element, the M2 element, and an excessive Licontent a, and the 32e site is occupied by O, a seat occupancy and anatomic displacement parameter B on each site were fixed to 1, and thecalculation was repeatedly performed until Rwp and S which represent thedegree of coincidence of an observed intensity with a calculatedintensity converged.

The observed intensity and the calculated intensity are sufficientlycoincident, which means that the obtained sample is not limited to thespace group, and there is a high reliability for the obtained sample tohave a spinel-type crystal structure.

=XRD Measurement Conditions 1=

X-ray source: CuKα (line focus), wavelength: 1.541836 Å

Operation axis: 2θ/θ, measurement method: continuous, counting unit: cps

Initiation angle: 15.0°, termination angle: 120.0°, number ofintegration times: 1 time

Sampling width: 0.01°, scanning speed: 1.0°/min

Voltage: 40 kV, current: 40 mA

Divergence slit: 0.2 mm, divergence vertical restriction slit: 10 mm

Scattering slit: opening, light-receiving slit: opening

Offset angle: 0°

Goniometer radius: 285 mm, optical system: focusing method

Attachment: ASC-48

Slit: slit for D/teX Ultra

Detector: D/teX Ultra

Incident-monochro: CBO

Ni-Kβ filter: None

Speed of revolution: 50 rpm

(Crystallite Size and Strain)

The measurement of an X-ray diffraction pattern for obtaining acrystallite size was performed under the following measurementconditions 2 using an X-ray diffractometer (D8 ADVANCE, manufactured byBruker AXS K.K.) using Cu-Kα rays.

Peaks in the X-ray diffraction pattern obtained in a range ofdiffraction angle 2θ=10 to 120° were analyzed using analysis software(product name “Topas Version 3”) to obtain a crystallite size and astrain of the sample.

Here, on the assumption that the crystal structure is attributed to acubic crystal of a space group Fd-3m (Origin Choice 2), and Li ispresent at the 8a site, Mn, the M1 element, the M2 element, and anexcessive Li content a are present at the 16d site, and the 32e site isoccupied by O, a parameter Beq. was fixed to 1, a fraction coordinateand a seat occupancy of O in the 32e site was set as a variable, and thecalculation was repeatedly performed until the indices Rwp and GOF,which represent the degree of coincidence of an observed intensity witha calculated intensity, converged to Rwp<10.0 and GOF<2.8 as a guide.The crystallite size and the strain were analyzed using Gauss functionto obtain the crystallite size and the strain.

=XRD Measurement Conditions 2=

Ray source: CuKα, operation axis: 2θ/θ, measurement method: continuous,counting unit: cps

Initiation angle: 10°, termination angle: 120°

Detector: PSD

Detector Type: VANTEC-1

High Voltage: 5,585 V

Discr. Lower Level: 0.25 V

Discr. Window Width: 0.15 V

Grid Lower Level: 0.075 V

Grid Window Width: 0.524 V

Flood Field Correction: Disabled

Primary radius: 250 mm

Secondary radius: 250 mm

Receiving slit width: 0.1436626 mm

Divergence slit: 0.5°

Filament Length: 12 mm

Sample Length: 25 mm

Receiving Slit Length: 12 mm

Primary Sollers: 2.623°

Secondary Sollers: 2.623°

Lorentzian, 1/Cos: 0.004933548 Th

Voltage: 40 kV, current: 35 mA

(Specific Surface Area)

A specific surface area (SSA) of the sample obtained in each of Examplesand Comparative Example was measured as follows.

First, 2.0 g of the sample (powder) was weighed in a glass cell(standard cell) for an automatic specific surface area analyzer, Macsorb(manufactured by Mountech Co., Ltd.), and was set in an auto sampler.The inside of the glass cell was replaced by a nitrogen gas, and then aheat treatment was performed at 250° C. for 15 minutes in the nitrogengas atmosphere. Thereafter, it was cooled for 4 minutes while allowing amixed gas of nitrogen and helium to flow. After cooling, the sample(powder) was measured by a BET one-point method.

Here, as the adsorption gas in the cooling and measurement, a mixed gasof 30% of nitrogen and 70% of helium was used.

<Surface Analysis by XPS>

The particle surface of the sample obtained in each of Examples andComparative Example was analyzed using a QUANTUM 2000 that was an XPSapparatus manufactured by Ulvac-Phi, Inc. The conditions used for themeasurement were as follows.

Excitation X-rays: AlKα (1,486.6 eV)

Tube voltage: 20 kV

Tube current: 5.0 mA

X-ray irradiation area: 100 μmϕ

Measurement conditions: state and semi-quantitative narrow measurement

Pass energy: 23.5 eV

Measurement interval: 0.1 eV

The XPS data was analyzed using data analysis software (“Multipack Ver.6.1A”, manufactured by Ulvac-Phi, Inc.). The orbit to be used for thecalculation was determined for each element as described below, and theanalysis was then performed.

Li: 1s

Ni: 2p3

Nb: 3d

Mn: 2p1

Ti: 2p3

C: 1s

O: 1s

The element ratio calculated in the above was confirmed by taking intoconsideration the interference of the LMM peak of Ni and comparing withthe compositional ratio of the above-mentioned chemical analysis result.

More specifically, in regard to the sample obtained in each of Examplesand Comparative Example, the surface of the sample particles wasanalyzed under the aforementioned conditions by using XPS, and the ratio(Li/Nb) of the peak intensity of the peak of Li relative to the peakintensity of the peak of Nb was determined from the obtained X-rayphotoelectron spectroscopic spectrum.

Here, by using XPS, the elemental component in the depth to about 5 nmfrom the particle surface can be quantitatively analyzed.

<Observation of Halo Pattern by Selected Area Electron Diffraction>

An electron diffraction was acquired from an area of about 100 nm indiameter under the conditions of an acceleration voltage of 200 kV and aselected area aperture size of 10 μm by using a transmission electronmicroscope (JEM-ARM200F, manufactured by JEOL Ltd.) to thereby observethe presence or absence of a halo pattern as shown in FIG. 2.

When the halo pattern can be observed, it can be confirmed that thecompound present on the surface of the sample obtained in each ofExamples and Comparative Example is an amorphous compound.

Here, the scale bar shown in FIG. 2 is a scale bar in the reciprocallattice space.

(Amount of Carbonate Ions: Amount of CO₃ ²⁻)

0.48 g of the sample obtained in each of Examples and ComparativeExample was introduced into 48 ml of pure water and stirred for 5minutes, and the resulting liquid was then filtered. Ion chromatographymeasurement was performed on the liquid from which lithium carbonate wasextracted as described above to determine an amount of CO₃ ²⁻ ions.

Here, the measurement was performed at 35° C. by using a Dionex ICS-2000manufactured by Thermo Fisher Scientific K.K. as a measurementapparatus, a Dionex IonPac AS17-C as a column, and a potassium hydroxideas a carrier liquid (eluent).

The amount of carbonate ions (amount of CO₃ ²⁻) (wt %) contained in thesample is shown in Table 1.

<Production and Evaluation of All Solid-State Lithium Secondary Battery>

A positive electrode mixture was prepared using the sample obtained ineach of Examples and Comparative Example and a solid electrolyte toproduce an all solid-state lithium secondary battery (all solid Gr/5V-class positive electrode active substance cell), and the batterycharacteristics were then evaluated (evaluations of rate characteristicsand cycle characteristics).

(Material)

The sample produced in each of Examples and Comparative Example was usedas a positive electrode active substance, a graphite (Gr) powder wasused as a negative electrode active substance, and a powder representedby a compositional formula: Li5.8PS4.8Cl1.2 was used as a solidelectrolyte powder.

The positive electrode mixture powder was prepared by mixing thepositive electrode active substance (sample) produced in each ofExamples and Comparative Example, the solid electrolyte powder, and aconductive material (acetylene black) powder in a ratio of 60:30:10 byusing a mortar.

The negative electrode mixture powder was prepared by mixing thegraphite (Gr) powder and the solid electrolyte powder in a ratio of50:50 by using a mortar.

(Production of All Solid-State Lithium Secondary Battery)

13 mg of the positive electrode mixture powder (sample) was filled in aninsulated tube (ϕ9 mm) for sealed-type cell, and was uniaxially moldedat 368 MPa to produce a positive electrode mixture powder pellet. Theobtained positive electrode mixture powder pellet was moved into aninsulated tube (ϕ10.5 mm) for sealed-type cell, and 50 mg of the solidelectrolyte powder was filled onto the positive electrode mixture powderpellet.

Next, the solid electrolyte powder was uniaxially molded at 184 MPaalong with the positive electrode mixture powder pellet. Further, 10 mgof the negative electrode mixture powder was filled onto the solidelectrolyte, and was uniaxially molded at 551 MPa. Then, they werefastened with pressuring screws to produce an all solid-state lithiumsecondary battery.

(Evaluation of Battery Characteristics)

The battery characteristics were evaluated after introducing the allsolid-state lithium secondary battery cell into an environmental testermaintained at 25° C. and connecting with a charge-discharge measurementapparatus. At this time, the charging was performed in a CC-CV mode atthe upper limit voltage of 5.0 V, and the discharging was performed in aCC mode at the lower limit voltage of 3.0 V.

The charging and the discharging were repeated at the current density of0.1 C for the first cycle to the third cycle. At the 4th cycle, thecharging was performed at the current density of 0.2 C, and thedischarging was performed at the current density of 2.0 C. Then, for the5th cycle to the 51st cycle, the charging and the discharging wererepeated at the current density of 0.1 C.

Here, the discharge capacity at the third cycle is shown in Table 1 as“3rd discharge capacity”.

In addition, based on the discharge curve at the third cycle, when theinitial stage of discharge is expressed as DOD 0% and the final stage ofdischarge is expressed as DOD 100%, the average value of the voltage inthe discharge period from DOD 0% to DOD 50% is shown in Table 1 as“operating potential (DOD 0% to 50%)”.

The value of “rate characteristics (2 C/0.1 C)” is expressed by aquotient obtained by dividing a discharge capacity at the 4th cycle by adischarge capacity at the second cycle. The result is shown in Table 1as a relative value when the value in Example 3 is set to 100.

The value of “operating potential retention rate (2 C/0.1 C)” isexpressed by a quotient obtained by calculating the average value of thevoltage in the discharge period from DOD 0% to DOD 50% at the time ofthe fourth cycle discharge and dividing the average value by theoperating potential (DOD 0% to 50%) at the third cycle. The result isshown in Table 1 as a relative value when the value in Example 5 is setto 100.

The value of “capacity retention rate index” is expressed by a quotientobtained by dividing a discharge capacity at the 51st cycle by adischarge capacity at the second cycle, and the result is shown in Table1 as a relative value when the value in Comparative Example 1 is set to100.

TABLE 1 Comparative Example 1 Example 2 Example 3 Example 4 Example 5Example 6 Example 7 Example 18 Example 1 Li x 1.04 0.7 1.08 1.04 1.051.05 1.05 1.04 1.01 M1 y 0.41 0.3

0.41 0.40 0.40 0.38 0.42 0.44 0.51 M

-

- 1.35 1.35 1.31 1.37 1.37 1.36 1.32 1.32 1.48 y-z M2 Z 0.20 0.19 0.200.19 0.18 0.20 0.20 0.20 0.00 Element Species M1 Ni Ni Ni Ni Ni Ni Ni NiNi Substitution Element — Ti, Al Ti Ti Ti Ti,

o Ti, Mg Ti Ti — Species M2 Secondary Particle μm 4.64 4.

3 4.55 4.

8 4.45 4.77 3.8

4.

5 17.26 Diameter (D50) (

mode diameter − % 0.22 8.1 1.7 1.2 5.0 5.4 0.2

10.0 6.7 D50

mode diameter) * 100

mode diameter − % 38 45 43 43 3

38 38 47

D10

mode diameter) * 100) Average Primary — 0.3

0.27 0.24 0.25 0.28 0.28 0.24 0.55 0.3

Particle Diameter/ D50 Crystallite Size nm 155 145 134 144 138 144 124152 215 Crystallite Size/ — 0.08 0.12 0.12 0.12 0.11 0.11 0.13 0.0

0.04 Average Primary Particle Diameter Mode Diameter μm 4.63 5.04 4.

3 5.04 4.24 5.04 3.88 5.

0 18.50 Average Primary μm 1.6

1.25 1.08 1.23 1.25 1.34 0.84 2.70 5.1

Particle Diameter D

n μm 1.78 1.50 1.50 1.0

1.26 1.6

1.26 1.2

3.00 Stain — 0.04 0.0

0.08 0.06 0.07 0.0

0.0

0.08 0.00 D10 μm 2.8

2.78 2.66 2.85 2.58 3.14 2.42 2.81 8.22 Specific Surface Area m²/g 2.32.7 3.0 2.7 3.0 2.2 3.0 4.0 0.2 Presence or Absence — present presentpresent present present present present present — of Halc Pattern Li/Nb(Analysis by — 1.58 2.01 2.

0 2.88 0.80 1.20 1.01 1.01 — XP3) Amount of C

32

% 0.1 0.4 1.5 0.5 0.2 0.1 0.3 0.5 0.0 3rd Discharge mAh/g 124 124 121103 105 113 118 107 1.3 Capacity Operating Potential V 4.

4.7 4.6 4.

4.5 4.5 4.

4.5 3.5 (DOD 0% to 50%) Rate Characteristics — 11

116 100 112 106 130 158 146 — (2C/0.1C) Operating Potential — 104 103 10

107 100 105 109 104 — Retention Rate (2C/0.1C) Capacity Retention — 181182 141 17

191 180 197 198 100 Rate Index

indicates data missing or illegible when filed

(Consideration)

In any of Examples 1 to 8, from the results of XRD measurements, ananalysis result in which the obtained lithium manganese-containingcomposite oxide was a 5 V-class spinel which was fitted to a crystalstructure model of a cubic crystal of a space group Fd-3m (Origin Choice2), wherein Rwp and S which represented the degree of coincidence of anobserved intensity with a calculated intensity were Rwp<10 or S<2.5, wasobtained. In addition, from the results of the battery performanceevaluation tests, it is confirmed that the obtained lithiummanganese-containing composite oxide had an operating potential of 4.5 Vor more at a metal Li reference potential.

Further, since the ratio of crystallite size/average primary particlediameter was less than 1, it is confirmed that the primary particleswere composed of a polycrystal in the present core particles of thepositive electrode active substance (sample) in any of Examples 1 to 8.

From the results of Examples described above and the results of thetests which have been so far conducted, by having a structure in whichthe surface of the present core particles composed of the spinel-typecomposite oxide containing Li, Mn, O, and two or more elements otherthan these is coated with the amorphous compound containing Li, A (Arepresents one element or a combination of two or more elements selectedfrom the group consisting of Ti, Zr, Ta, Nb, Zn, W, and Al), and O;having the primary particles of the present core particles composed of apolycrystal; having a D50 in the volume-based particle size distributionmeasurement of 0.5 to 9 μm; specifying the relationship among the modediameter, D50, and D10; and specifying the relationship between theaverage primary particle diameter and D50, the dispersibility of theprimary particles can be enhanced, and further, by making the particlesize distribution close to the normal distribution and sharp, theoperating voltage during discharge can be maintained high, and the ratecharacteristics and the cycle characteristics can be effectivelyimproved. It can be considered that this is made as a result ofachieving both the lithium ion conductivity improvement and theresistance suppression and reducing the contact resistance between thepositive electrode active substance and the solid electrolyte.

From such a view point, in regard to the positive electrode activesubstance having a structure in which the surface of the present coreparticles containing at least Li, Mn, 0, and two or more elements otherthan these is coated with the amorphous compound containing Li, A (Arepresents one element or a combination of two or more elements selectedfrom the group consisting of Ti, Zr, Ta, Nb, Zn, W, and Al), and O; andhaving an operating potential of 4.5 V or more at a metal Li referencepotential, it is found that the D50 according to a measurement of avolume-based particle size distribution obtained via measurements by alaser diffraction scattering-type particle size distribution measurementmethod is preferably 0.5 to 9 μm, the percentage of the ratio of theabsolute value of the difference between the mode diameter and the D50relative to the mode diameter ((|mode diameter−D50|/mode diameter)×100)is preferably 0 to 25%, and the percentage of the ratio of the absolutevalue of the difference between the mode diameter and the D10 relativeto the mode diameter ((|mode diameter−D10|/mode diameter)×100) ispreferably 20 to 58%.

It is also found that the ratio of average primary particlediameter/D50, which is calculated from the average primary particlediameter calculated from the SEM image and the D50, is preferably 0.20to 0.99.

As for the structure where the LiAO compound is present on the surfaceof the present core particles in the above Examples, only Nb is used asthe A element in Examples, but Nb and Ti, Zr, Ta, Zn, W, and Al arecommon in that they are valve metals, and it can be considered that thesame effect can be obtained.

1. A positive electrode active substance for an all solid-state lithiumsecondary battery, having an operating potential of 4.5 V or more at ametal Li reference potential, wherein a surface of present coreparticles composed of a spinel-type lithium manganese-containingcomposite oxide containing at least Li, Mn, O, and two or more elementsother than Li, Mn, and O is coated with an amorphous compound containingLi, A, where A represents one element or a combination of two or moreelements selected from the group consisting of Ti, Zr, Ta, Nb, Zn, W,and Al, and O; and primary particles of the present core particles arecomposed of a polycrystal; wherein, with regard to a D50, a modediameter, and a D10 of the positive electrode active substance accordingto a measurement of a volume-based particle size distribution obtainedvia measurements by a laser diffraction scattering-type particle sizedistribution measurement method, the D50 is 0.5 to 9 μm, a percentage ofa ratio of the absolute value of the difference between the modediameter and the D50 relative to the mode diameter, (|modediameter−D50|/mode diameter)×100, is 0 to 25%, a percentage of a ratioof the absolute value of the difference between the mode diameter andthe D10 relative to the mode diameter, (|mode diameter−D10|/modediameter)×100, is 20 to 58%; and wherein a ratio, average primaryparticle, diameter/D50 of an average primary particle diameter of thepositive electrode active substance, which is calculated from ascanning-type electron microscope (SEM) image obtained by scanning-typeelectron microscope (SEM), relative to the D50 is 0.20 to 0.99.
 2. Apositive electrode active substance for an all solid-state lithiumsecondary battery, having an operating potential of 4.5 V or more at ametal Li reference potential, wherein the surface of present coreparticles composed of a spinel-type lithium manganese-containingcomposite oxide containing at least Li, Mn, O, and two or more elementsother than Li, Mn, and O is coated with an amorphous compound containingLi, A, where A represents one element or a combination of two or moreelements selected from the group consisting of Ti, Zr, Ta, Nb, Zn, W,and Al, and O; a crystallite size of the positive electrode activesubstance is 80 to 490 nm; and a ratio, crystallite size/average primaryparticle diameter, of the crystallite size relative to an averageprimary particle diameter of the positive electrode active substance,which is calculated from a scanning-type electron microscope (SEM) imageobtained by scanning-type electron microscope (SEM), is 0.01 to 0.32;wherein, with regard to a D50, a mode diameter, and a D10 of thepositive electrode active substance, the D50 is 0.5 to 9 μm, apercentage of a ratio of the absolute value of the difference betweenthe mode diameter and the D50 relative to the mode diameter, (|modediameter−D50|/mode diameter)×100, is 0 to 25%, a percentage of a ratioof the absolute value of the difference between the mode diameter andthe D10 relative to the mode diameter, ((|mode diameter−D100|/modediameter)×100, is 20 to 58%; and wherein a ratio, average primaryparticle, diameter/D50 of the average primary particle diameter of thepositive electrode active substance relative to the D50 is 0.20 to 0.99.3. The positive electrode active substance for an all solid-statelithium secondary battery according to claim 1, wherein the molar ratio,Li/A, of Li relative to the A element in the positive electrode activesubstance surface, as obtained by X-ray photoelectron spectroscopy(XPS), is 0.5 to 3.5.
 4. The positive electrode active substance for anall solid-state lithium secondary battery according to claim 1, whereinthe spinel-type lithium manganese-containing composite oxide isrepresented by a general formula[Li_(x)(M1_(y)M2_(z)Mn_(2-x-y-z))O_(4-δ)], wherein 1.00≤x≤1.20,0.20≤y≤1.20, 0<z≤0.5, 0≤δ≤0.2, M1 represents one element or acombination of two or more elements selected from the group consistingof Ni, Co, and Fe, and M2 represents one element or a combination of twoor more elements selected from the group consisting of Na, Mg, Al, P, K,Ca, Ti, V, Cr, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce.
 5. Thepositive electrode active substance for an all solid-state lithiumsecondary battery according to claim 1, wherein the spinel-type lithiummanganese-containing composite oxide is represented by a general formula[Li_(x)(Ni_(y)M_(z)Mn_(2-x-y-z))O_(4-δ)], wherein 1.00≤x≤1.20,0.20≤y≤0.70, 0<z≤0.5, 0≤δ≤0.2, and M represents one element or acombination of two or more elements selected from the group consistingof Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, In,Ta, W, Re, and Ce.
 6. The positive electrode active substance for an allsolid-state lithium secondary battery according to claim 1, wherein themode diameter according to a measurement of a volume-based particle sizedistribution obtained via measurements by a laser diffractionscattering-type particle size distribution measurement method is 0.4 to11 μm.
 7. The positive electrode active substance for an all solid-statelithium secondary battery according to claim 1, wherein the averageprimary particle diameter which is calculated from a scanning-typeelectron microscope (SEM) image obtained by a scanning-type electronmicroscope (SEM) is 0.3 to 5.0 μm.
 8. The positive electrode activesubstance for an all solid-state lithium secondary battery accordingclaim 1, wherein a Dmin in a result of measuring a volume-based particlesize distribution obtained via measurements by a laser diffractionscattering-type particle size distribution measurement method is 0.1 to2.0 μm.
 9. The positive electrode active substance for an allsolid-state lithium secondary battery according to claim 1, wherein, inan X-ray diffraction pattern measured by a powder X-ray diffractometer(XRD), a value of a strain obtained by Rietveld analysis is 0.00 to0.35.
 10. An all solid-state lithium secondary battery, comprising thepositive electrode active substance for an all solid-state lithiumsecondary battery according to claim 1 as a positive electrode activesubstance.
 11. An all solid-state lithium secondary battery, comprisingthe positive electrode active substance for an all solid-state lithiumsecondary battery according to claim 2 as a positive electrode activesubstance.
 12. The positive electrode active substance for an allsolid-state lithium secondary battery according to claim 2, wherein themolar ratio, Li/A, of Li relative to the A element in the positiveelectrode active substance surface, as obtained by X-ray photoelectronspectroscopy (XPS), is 0.5 to 3.5.
 13. The positive electrode activesubstance for an all solid-state lithium secondary battery accordingclaim 2, wherein the spinel-type lithium manganese-containing compositeoxide is represented by a general formula[Li_(x)(M1_(y)M2_(z)Mn_(2-x-y-z))O_(4-δ)], wherein 1.00≤x≤1.20,0.20≤y≤1.20, 0<z≤0.5, 0≤δ≤0.2, M1 represents one element or acombination of two or more elements selected from the group consistingof Ni, Co, and Fe, and M2 represents one element or a combination of twoor more elements selected from the group consisting of Na, Mg, Al, P, K,Ca, Ti, V, Cr, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce.
 14. Thepositive electrode active substance for an all solid-state lithiumsecondary battery according claim 3, wherein the spinel-type lithiummanganese-containing composite oxide is represented by a general formula[Li_(x)(M1_(y)M2_(z)Mn_(2-x-y-z))O_(4-δ)], wherein 1.00≤x≤1.20,0.20≤y≤1.20, 0<z≤0.5, 0≤δ≤0.2, M1 represents one element or acombination of two or more elements selected from the group consistingof Ni, Co, and Fe, and M2 represents one element or a combination of twoor more elements selected from the group consisting of Na, Mg, Al, P, K,Ca, Ti, V, Cr, Cu, Ga, Y, Zr, Nb, Mo, In, Ta, W, Re, and Ce.
 15. Thepositive electrode active substance for an all solid-state lithiumsecondary battery according claim 2, wherein the spinel-type lithiummanganese-containing composite oxide is represented by a general formula[Li_(x)(Ni_(y)M_(z)Mn_(2-x-y-z))O_(4-δ)], wherein 1.00≤x≤1.20,0.20≤y≤0.70, 0<z≤0.5, 0≤δ≤0.2, and M represents one element or acombination of two or more elements selected from the group consistingof Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr, Nb, Mo, In,Ta, W, Re, and Ce.
 16. The positive electrode active substance for anall solid-state lithium secondary battery according claim 3, wherein thespinel-type lithium manganese-containing composite oxide is representedby a general formula [Li_(x)(Ni_(y)M_(z)Mn_(2-x-y-z))O_(4-δ)], wherein1.00≤x≤1.20, 0.20≤y≤0.70, 0<z≤0.5, 0≤δ≤0.2, and M represents one elementor a combination of two or more elements selected from the groupconsisting of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Fe, Co, Cu, Ga, Y, Zr,Nb, Mo, In, Ta, W, Re, and Ce.
 17. The positive electrode activesubstance for an all solid-state lithium secondary battery accordingclaim 2, wherein the mode diameter according to a measurement of avolume-based particle size distribution obtained via measurements by alaser diffraction scattering-type particle size distribution measurementmethod is 0.4 to 11 μm.
 18. The positive electrode active substance foran all solid-state lithium secondary battery according claim 3, whereinthe mode diameter according to a measurement of a volume-based particlesize distribution obtained via measurements by a laser diffractionscattering-type particle size distribution measurement method is 0.4 to11 μm.
 19. The positive electrode active substance for an allsolid-state lithium secondary battery according claim 4, wherein themode diameter according to a measurement of a volume-based particle sizedistribution obtained via measurements by a laser diffractionscattering-type particle size distribution measurement method is 0.4 to11 μm.
 20. The positive electrode active substance for an allsolid-state lithium secondary battery according claim 5, wherein themode diameter according to a measurement of a volume-based particle sizedistribution obtained via measurements by a laser diffractionscattering-type particle size distribution measurement method is 0.4 to11 μm.